ramips-mt76x8: add support for TP-Link TL-WR902AC v3

TP-Link TL-WR902AC v3 is a pocket-size dual-band (AC750) router
based on MediaTek MT7628N + MT7650E.

Specification:
- MediaTek MT7628N/N (580 Mhz)
- 64 MB of RAM
- 8 MB of FLASH
- 2T2R 2.4 GHz and 1T1R 5 GHz
- 1x 10/100 Mbps Ethernet

docs/user/supported_devices.rst

@@ -350,6 +350,7 @@ ramips-mt76x8
 
   - TL-MR3420 v5
   - TL-WR841N v13
+  - TL-WR902AC v3
   - Archer C50 v3
   - Archer C50 v4
 

targets/ramips-mt76x8

@@ -43,6 +43,12 @@ device('tp-link-tl-wr841n-v13', 'tl-wr841n-v13', {
 	},
 })
 
+device('tp-link-tl-wr902ac-v3', 'tplink_tl-wr902ac-v3', {
+	factory = false,
+	extra_images = {
+		{'-squashfs-tftp-recovery', '-bootloader', '.bin'},
+	},
+})
 
 -- VoCore 2