ath79: add support for TP-Link CPE510 v1

ath79: add support for TP-Link CPE510 v1

TP-Link CPE510-v1 is an outdoor wireless CPE for 5 GHz with
two Ethernet ports based on Atheros AR9334

Specifications:
 - 560/450/225 MHz (CPU/DDR/AHB)
 - 2x 10/100 Mbps Ethernet, 1x PoE-in, 1x PoE-out
 - 64 MB of DDR2 RAM
 - 8 MB of SPI-NOR Flash
 - 2T2R 5 GHz
 - 13 dBi built-in antenna
 - Power, LAN0, LAN1 green LEDs
 - 4x green RSSI LEDs

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 address:192.168.0.254

Based on the work of Paul Wassi <p.wassi@gmx.at>

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>