I do not have access to serial console right now but here is the initramfs bootlog:
[ 0.000000] Linux version 4.9.109 (buildbot@crazyhorse) (gcc version 7.3.0 (OpenWrt GCC 7.3.0 r7199-70f4845) ) #0 Fri Jun 22 07:43:56 2018
[ 0.000000] bootconsole [early0] enabled
[ 0.000000] CPU0 revision is: 00019374 (MIPS 24Kc)
[ 0.000000] SoC: Qualcomm Atheros QCA9533 ver 2 rev 0
[ 0.000000] Determined physical RAM map:
[ 0.000000] memory: 04000000 @ 00000000 (usable)
[ 0.000000] User-defined physical RAM map:
[ 0.000000] memory: 04000000 @ 00000000 (usable)
[ 0.000000] Initrd not found or empty - disabling initrd
[ 0.000000] Primary instruction cache 64kB, VIPT, 4-way, linesize 32 bytes.
[ 0.000000] Primary data cache 32kB, 4-way, VIPT, cache aliases, linesize 32 bytes
[ 0.000000] Zone ranges:
[ 0.000000] Normal [mem 0x0000000000000000-0x0000000003ffffff]
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000000000000-0x0000000003ffffff]
[ 0.000000] Initmem setup node 0 [mem 0x0000000000000000-0x0000000003ffffff]
[ 0.000000] On node 0 totalpages: 16384
[ 0.000000] free_area_init_node: node 0, pgdat 804d9674, node_mem_map 81000020
[ 0.000000] Normal zone: 128 pages used for memmap
[ 0.000000] Normal zone: 0 pages reserved
[ 0.000000] Normal zone: 16384 pages, LIFO batch:3
[ 0.000000] pcpu-alloc: s0 r0 d32768 u32768 alloc=1*32768
[ 0.000000] pcpu-alloc: [0] 0
[ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 16256
[ 0.000000] Kernel command line: no-uart no-buzzer no-nand parts=1 boot_part_size=16777216 gpio=8520495 HZ=325000000 mem=64M kmac=64:D1:54:7D:E4:B0 board=wap-lte board=wap-lte hw_opt=00684001 boot=0 mlc=11 console=ttyS0,115200 rootfstype=squashfs noinitrd
[ 0.000000] PID hash table entries: 256 (order: -2, 1024 bytes)
[ 0.000000] Dentry cache hash table entries: 8192 (order: 3, 32768 bytes)
[ 0.000000] Inode-cache hash table entries: 4096 (order: 2, 16384 bytes)
[ 0.000000] Writing ErrCtl register=00000000
[ 0.000000] Readback ErrCtl register=00000000
[ 0.000000] Memory: 57652K/65536K available (3583K kernel code, 156K rwdata, 844K rodata, 2064K init, 217K bss, 7884K reserved, 0K cma-reserved)
[ 0.000000] SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[ 0.000000] NR_IRQS:51
[ 0.000000] Clocks: CPU:650.000MHz, DDR:600.000MHz, AHB:300.000MHz, Ref:25.000MHz
[ 0.000000] clocksource: MIPS: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 5880801374 ns
[ 0.000009] sched_clock: 32 bits at 325MHz, resolution 3ns, wraps every 6607641598ns
[ 0.008875] Calibrating delay loop... 432.53 BogoMIPS (lpj=2162688)
[ 0.071946] pid_max: default: 32768 minimum: 301
[ 0.077295] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.084807] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.095506] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
[ 0.106694] futex hash table entries: 256 (order: -1, 3072 bytes)
[ 0.114785] NET: Registered protocol family 16
[ 0.123499] MIPS: machine is MikroTik RouterBOARD wAP R-2nD
[ 0.386411] clocksource: Switched to clocksource MIPS
[ 0.393207] NET: Registered protocol family 2
[ 0.399082] TCP established hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.407053] TCP bind hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.414274] TCP: Hash tables configured (established 1024 bind 1024)
[ 0.421600] UDP hash table entries: 256 (order: 0, 4096 bytes)
[ 0.428269] UDP-Lite hash table entries: 256 (order: 0, 4096 bytes)
[ 0.435638] NET: Registered protocol family 1
[ 0.440658] PCI: CLS 0 bytes, default 32
[ 2.566421] random: fast init done
[ 2.603938] Crashlog allocated RAM at address 0x3f00000
[ 2.610870] workingset: timestamp_bits=30 max_order=14 bucket_order=0
[ 2.625073] squashfs: version 4.0 (2009/01/31) Phillip Lougher
[ 2.631728] jffs2: version 2.2 (NAND) (SUMMARY) (LZMA) (RTIME) (CMODE_PRIORITY) (c) 2001-2006 Red Hat, Inc.
[ 2.728536] io scheduler noop registered
[ 2.732986] io scheduler deadline registered (default)
[ 2.739263] Serial: 8250/16550 driver, 16 ports, IRQ sharing enabled
[ 2.749035] console [ttyS0] disabled
[ 2.773221] serial8250.0: ttyS0 at MMIO 0x18020000 (irq = 11, base_baud = 1562500) is a 16550A
[ 2.783019] console [ttyS0] enabled
[ 2.790567] bootconsole [early0] disabled
[ 2.804340] m25p80 spi0.0: unrecognized JEDEC id bytes: ef, 70, 18
[ 2.811732] libphy: Fixed MDIO Bus: probed
[ 2.929922] libphy: ag71xx_mdio: probed
[ 3.558719] ag71xx-mdio.1: Found an AR934X built-in switch
[ 3.612255] eth0: Atheros AG71xx at 0xba000000, irq 5, mode:GMII
[ 3.619946] NET: Registered protocol family 10
[ 3.627621] NET: Registered protocol family 17
[ 3.632264] bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if you need this.
[ 3.645689] 8021q: 802.1Q VLAN Support v1.8
[ 3.664809] Freeing unused kernel memory: 2064K
[ 3.669523] This architecture does not have kernel memory protection.
[ 3.689519] init: Console is alive
[ 3.693266] init: - watchdog -
[ 3.716263] kmodloader: loading kernel modules from /etc/modules-boot.d/*
[ 3.725663] kmodloader: done loading kernel modules from /etc/modules-boot.d/*
[ 3.743888] init: - preinit -
[ 3.955087] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[ 5.066849] random: procd: uninitialized urandom read (4 bytes read)
[ 5.587843] eth0: link up (1000Mbps/Full duplex)
[ 5.592644] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[ 7.104696] random: dropbearkey: uninitialized urandom read (32 bytes read)
[ 7.113281] random: dropbearkey: uninitialized urandom read (32 bytes read)
[ 10.325927] random: dropbearkey: uninitialized urandom read (32 bytes read)
[ 10.341710] random: dropbear: uninitialized urandom read (32 bytes read)
[ 18.216738] random: dropbear: uninitialized urandom read (32 bytes read)
[ 24.112750] random: dropbear: uninitialized urandom read (32 bytes read)
[ 25.804425] random: dropbear: uninitialized urandom read (32 bytes read)
[ 125.386452] random: crng init done
and ifconfig
root@(none):~# ifconfig
eth0 Link encap:Ethernet HWaddr 64:D1:54:7D:E4:B0
inet addr:192.168.1.1 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::66d1:54ff:fe7d:e4b0/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:831 errors:0 dropped:4 overruns:0 frame:0
TX packets:265 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:105339 (102.8 KiB) TX bytes:41450 (40.4 KiB)
Interrupt:5
FYC - this unit was LTE kit but I removed the modem before booting into initramfs -- when trying to run sysupgrade with modem installed unit would reboot into RouterOS.