ar71xx: add support for TP-Link TL-WR810N v2

TP-Link TL-WR810N v2 is a compact Wi-Fi router with two Ethernet ports.

Specification:

- QCA9533 (650 MHz)
- 32 MB RAM
- 8 MB Flash
- 300 Mbps Wi-Fi 2.4 GHz
- 2x 10/100 Mbps Ethernet (eth0, eth1)
- UART on testpads on PCB
- 1x LED (GPIO-controlled)
- 1x reset/WPS button
- 1x slide-switch with 2 GPIO inputs

Flash instructions:

- Flash as regular firmware update in Web UI
- Default: 192.168.0.254 / admin / admin
- Select *-factory.bin

When holding reset button during power-up, U-Boot requests a file
'wr810nv1_tp_recovery.bin' from TFTP server at 192.168.0.66

Signed-off-by: Paul Wassi <p.wassi@gmx.at>

target/linux/ar71xx/base-files/lib/upgrade/platform.sh

@@ -443,6 +443,7 @@ platform_check_image() {
 	tl-wr802n-v1|\
 	tl-wr802n-v2|\
 	tl-wr810n|\
+	tl-wr810n-v2|\
 	tl-wr840n-v2|\
 	tl-wr840n-v3|\
 	tl-wr841n-v1|\