Bonding - 802.3ad

Whether compilation of a kernel for support of bonding of the mode - 802.3ad is possible

this package might be of some help:
https://lede-project.org/packages/pkgdata/kmod-bonding

some info:
https://forum.openwrt.org/viewtopic.php?id=69209

off-topic but worth checking:

for ramips-rt305x

for support there shall be a bonding.ko module
root@LEDE:/lib/modules/4.4.71# uname -a
Linux LEDE 4.4.71 #0 Wed Jun 7 19:24:41 2017 mips GNU/Linux
root@LEDE:/lib/modules/4.4.71# ls -l | grep bonding
root@LEDE:/lib/modules/4.4.71# lsmod | grep bonding

In dd-wrt

~# lsmod
Module                  Size  Used by
bonding                81257  0 
...
...
vconfig add eth0 3
vconfig add eth0 4
ifconfig vlan3 up
ifconfig vlan4 up 
...

ifconfig
bond0     Link encap:Ethernet  HWaddr хх:хх:хх:хх:хх:xx 
          UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1
...
vlan3     Link encap:Ethernet  HWaddr хх:хх:хх:хх:хх:xx 
          UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1
vlan4     Link encap:Ethernet  HWaddr хх:хх:хх:хх:хх:xx 
          UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1
...
~# cat /sys/class/net/bond0/bonding/mode 
802.3ad 4
~# cat /sys/class/net/bond0/bonding/slaves
vlan4 vlan3
...

Logically, there is always a possibility that bonding.ko had been stripped away to save space due to low demand. Maybe you should try following the white rabbit with a custom build: How to build with the official release configuration (and a small patch)?

There was a wish to try on Dlink-620A1 (RT3052F) on the second device already is there is an opportunity to use bonding.

3123.8 KB = dir-620-a1-initramfs-kernel.bin
3328.2 KB = dir-620-a1-squashfs-sysupgrade.bin
https://downloads.lede-project.org/releases/17.01.2/targets/ramips/rt305x/

Technical Data: Dlink Dir-620A1
Ralink RT3052F@384MHz / Ram 32МБ / flash 8МБ /4 LAN + 1 WAN /2x2 2.4Ghz / 802.11n / 300 Мбит/с / USB 1 port 2.0

root@LEDE:~# dmesg
[    0.000000] Linux version 4.4.71 (buildbot@builds-02.infra.lede-project.org) (gcc version 5.4.0 (LEDE GCC 5.4.0 r3102-0224e32) ) #0 Wed Jun 7 19:24:41 2017
[    0.000000] SoC Type: Ralink RT3052 id:1 rev:3
[    0.000000] bootconsole [early0] enabled
[    0.000000] CPU0 revision is: 0001964c (MIPS 24KEc)
[    0.000000] MIPS: machine is D-Link DIR-620 A1
...
[    0.753928] rt3050-esw 10110000.esw: link changed 0x04
[    0.767741] mtk_soc_eth 10100000.ethernet eth0: mediatek frame engine at 0xb0100000, irq 5
[    0.785217] rt2880_wdt 10000120.watchdog: Initialized
[    0.797446] NET: Registered protocol family 10
[    0.812361] NET: Registered protocol family 17
[    0.821557] bridge: automatic filtering via arp/ip/ip6tables has been deprecated. Update your scripts to load br_netfilter if you need this.
[    0.847023] 8021q: 802.1Q VLAN Support v1.8
...
[    3.996651] 8021q: adding VLAN 0 to HW filter on device eth0