ath79: add support for TP-Link CPE710-v2

ath79: add support for TP-Link CPE710-v2

TP-Link CPE710-v2 is an outdoor wireless CPE for 5 GHz with one Ethernet
port based on the AP152 reference board. Compared to the CPE710-v1, the
only change observed in hardware is that the mdio address of the ethernet
physical changed from 0x4 to 0x0.

Specifications:
- SoC: QCA9563-AL3A MIPS 74kc @ 775MHz, AHB @ 258MHz
- RAM: 128MiB DDR2 @ 650MHz
- Flash: 16MiB SPI NOR Based on the GD25Q128
- Wi-Fi 5Ghz: ath10k chip (802.11ac for up to 867Mbps on 5GHz wireless
  data rate), based on the QCA9896
- Ethernet: one 1GbE port
- 23dBi high-gain directional 2×2 MIMO parabolic antenna
- Power, LAN, WLAN5G Blue 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
30-40 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

Signed-off-by: Tim Noack <tim@noack.id>
Link: https://github.com/openwrt/openwrt/pull/16637
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>