ath79: add support for TP-Link CPE610 v2

ath79: add support for TP-Link CPE610 v2

TP-Link CPE610 v2 is an outdoor wireless CPE for 5 GHz with
one Ethernet port based on Atheros AR9344

Specifications:
 - 560/450/225 MHz (CPU/DDR/AHB)
 - 1x 10/100 Mbps Ethernet
 - 64 MB of DDR2 RAM
 - 8 MB of SPI-NOR Flash
 - 23dBi high-gain directional 2×2 MIMO antenna and a
   dedicated metal reflector
 - Power, LAN, WLAN5G green LEDs
 - 3x green RSSI LEDs

Flashing instructions:
 Flash factory image through stock firmware WEB UI
 or through TFTP
 To get to TFTP recovery just hold reset button while powering on for
 around 4-5 seconds and release.
 Rename factory image to recovery.bin
 Stock TFTP server IP:192.168.0.100
 Stock device TFTP adress:192.168.0.254

Signed-off-by: Andrew Cameron <apcameron@softhome.net>