Support for Asus WIreless AC1300 RT-ACRH13

ipq806x: add support for ASUS RT-AC58U/RT-ACRH13

 - hardware highlights:
    SOC:    IPQ4019 / QCA Dakota
    CPU:    Quad-Core ARMv7 Processor rev 5 (v7l) Cortex-A7
    DRAM:   128 MiB DDR3L-1066 @ 537 MHz (1074?) NT5CC64M16GP-DI
    NOR:    2 MiB Macronix MX25L1606E (for boot, QSEE)
    NAND:   128 MiB Winbond W25NO1GVZE1G (cal + kernel + root, UBI)
    ETH:    Qualcomm Atheros QCA8075 Gigabit Switch (4 x LAN, 1 x WAN)
    USB:    1 x 3.0 (via Synopsys DesignWare DWC3 controller in the SoC)
    WLAN1:  Qualcomm Atheros QCA4019 2.4GHz 802.11bgn 2:2x2
    WLAN2:  Qualcomm Atheros QCA4019 5GHz 802.11a/n/ac 2:2x2
    INPUT:  one Reset and one WPS button
    LEDS:   Status, WAN, WIFI1/2, USB and LAN (one blue LED for each)

 - Install with two steps(-must-):
    1. install factory.trx image, this can be done via the web-interface
    2. after the factory.trx installation, install the sysupgrade.bin
       do this via luci web ui or ssh, it is recommended not to keep the configuration

 - Revert back to stock:
    1. login ssh to openwrt and execute: sysupgrade -F /bin/busybox
    2. after that system reboot to recovery mode, computer set static IP
       192.168.1.70, connect to lan port, use tftp send the RT-AC58U.trx
       to 192.168.1.1. like:
       tftp 192.168.1.1 put RT-AC58U.trx

code:

anyone help to test this
firmware rom binary downloads:
https://router-sh.ptpt52.com/rom/