ramips: add support for HiWiFi HC5761A

HiWiFi HC5761A is an "MT7628AN variant" of HC5761

Specifications:
- MediaTek MT7628AN 580MHz
- 128 MB DDR2 RAM
- 16 MB SPI Flash
- 2.4G MT7628AN 802.11bgn 2T2R 300Mbps
- 5G MT7610EN 802.11ac 433Mbps
- 3x 10/100 Mbps Ethernet

Flash instruction:
1. Get SSH access to the router
2. SSH to router with `ssh -p 1022 root@192.168.199.1`, The SSH password is the same as the webconfig one
3. Upload OpenWrt sysupgrade firmware into the router's `/tmp` folder with SCP
4. Run `mtd write /tmp/<filename> firmware`
5. reboot

Known bug:
- SD slot does not work (See PR 1500)

Signed-off-by: DENG Qingfang <dengqf6@mail2.sysu.edu.cn>

target/linux/ramips/base-files/etc/board.d/01_leds

@@ -208,6 +208,7 @@ hiwifi,hc5661)
 	set_wifi_led "$boardname:blue:wlan2g"
 	;;
 hiwifi,hc5661a|\
+hiwifi,hc5761a|\
 xzwifi,creativebox-v1)
 	ucidef_set_led_switch "internet" "internet" "$boardname:blue:internet" "switch0" "0x10"
 	;;

target/linux/ramips/base-files/etc/board.d/02_network

@@ -57,6 +57,7 @@ ramips_setup_interfaces()
 	firefly,firewrt|\
 	hilink,hlk-rm04|\
 	hiwifi,hc5661a|\
+	hiwifi,hc5761a|\
 	hiwifi,hc5962|\
 	mediatek,ap-mt7621a-v60|\
 	mediatek,mt7621-eval-board|\
@@ -597,6 +598,7 @@ ramips_setup_macs()
 	hiwifi,hc5661|\
 	hiwifi,hc5661a|\
 	hiwifi,hc5761|\
+	hiwifi,hc5761a|\
 	hiwifi,hc5861|\
 	hiwifi,hc5861b|\
 	hiwifi,hc5962)