ath79: add support for ASUS RP-AC51

ath79: add support for ASUS RP-AC51

Asus RP-AC51 Repeater
Category:
AC750 300+433 (OEM w. unstable driver)
AC1200 300+866 (OpenWrt w. stable driver)

Hardware specifications:
Board: AP147
SoC: QCA9531 2.4G b/g/n
WiFi: QCA9886 5G n/ac
DRAM: 128MB DDR2
Flash: gd25q128 16MB SPI-NOR
LAN/WAN: AR8229 1x100M
Clocks: CPU:650MHz, DDR:600MHz, AHB:200MHz

MAC addresses as verified by OEM firmware:
use address source
Lan/W2G *:C8 art 0x1002 (label)
5G *:CC art 0x5006

Installation:

Asus windows recovery tool:

install the Asus firmware restoration utility
unplug the router, hold the reset button while powering it on
release when the power LED flashes slowly
specify a static IP on your computer:
IP address: 192.168.1.75
Subnet mask 255.255.255.0
Start the Asus firmware restoration utility, specify the factory image
and press upload
Do not power off the device after OpenWrt has booted until the LED flashing.
TFTP Recovery method:

set computer to a static ip, 192.168.1.10
connect computer to the LAN 1 port of the router
hold the reset button while powering on the router for a few seconds
send firmware image using a tftp client; i.e from linux:
$ tftp
tftp> binary
tftp> connect 192.168.1.1
tftp> put factory.bin
tftp> quit

Signed-off-by: Tamas Balogh <tamasbalogh@hotmail.com>