ath79: prepare for 1-port TP-Link EAP2x5 devices

ath79: prepare for 1-port TP-Link EAP2x5 devices

TP-Link has developed a number of access points based on the AP152
reference board. In the EAP-series of 802.11ac access points, this
includes the following devices with one ethernet port:
* EAP225 v1/v2
* EAP225 v3
* EAP225-Outdoor v1
* EAP245 v1

Since the only differences between these devices are the ath10k wireless
radios and LEDs, a common base is provided for the overlapping support
requirements.

Hardware commonalities:
* SoC: QCA9563-AL3A MIPS 74kc v5.0 @ 775MHz, AHB @ 258MHz
* RAM: 128MiB DDR2 @ 650MHz
* Flash: 16MiB SPI NOR
* Wi-Fi 2.4GHz: provided by SoC
* Wi-Fi 5Ghz: ath10k chip on PCIe
* Ethernet: AR8033-AL1A, one 1GbE port (802.3at PoE)

Signed-off-by: Sander Vanheule <sander@svanheule.net>