ramips: add support for Netgear R6220

This patch adds support for the Netgear R6220, aka Netgear AC1200 and
R6220-100NAS.

Specification:
- SoC: MediaTek MT7621ST (880 MHz)
- Falsh: 128 MiB (Macronix MX30LF1G08AA-TI)
- RAM: 128 MiB (Nanya NT5CB64M16FP-DH)
- Wireless: MediaTek MT7603EN b/g/n , MediaTek MT7612EN an+ac
- LAN speed: 10/100/1000
- LAN ports: 4
- WAN speed: 10/100/1000
- WAN ports: 1
- Serial baud rate of Bootloader and factory firmware: 57600

Installation through telnet:
- Copy kernel.bin and rootfs.bin to a USB flash disk, plug to usb port
  on the router.
- Enable telnet with link: http://192.168.1.1/setup.cgi?todo=debug
  (login if required, default: admin password)
- You will see "Debug Enabled!"
- Telnet 192.168.1.1 and login with "root"
- ls /mnt/shares/ to find out path of your USB disk. 'myUdisk' for
  example.
- cd /mnt/shares/myUdisk
- mtd_write write rootfs.bin Rootfs
- mtd_write write kernel.bin Kernel
- reboot

nmrpflash can be used to recover to the netgear firmware if a broken
image was flashed.

Signed-off-by: Hanqing Wong <hquu@outlook.com>

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

@@ -291,6 +291,11 @@ px-4885)
 	set_wifi_led "$board:orange:wifi"
 	set_usb_led "$board:blue:storage"
 	;;
+r6220)
+	ucidef_set_led_netdev "wan" "wan" "$board:green:wan" eth0.2
+	set_wifi_led "$board:green:wifi"
+	set_usb_led "$board:green:usb"
+	;;
 re6500)
 	ucidef_set_led_default "power" "power" "$board:white:power" "1"
 	ucidef_set_led_default "wifi" "wifi" "$board:orange:wifi" "1"

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

@@ -95,6 +95,7 @@ ramips_setup_interfaces()
 	pbr-m1|\
 	psg1208|\
 	psg1218|\
+	r6220|\
 	sap-g3200u3|\
 	sk-wb8|\
 	vr500|\
@@ -394,6 +395,10 @@ ramips_setup_macs()
 		lan_mac=$(mtd_get_mac_binary factory 40)
 		wan_mac=$(mtd_get_mac_binary factory 46)
 		;;
+	r6220)
+		wan_mac=$(mtd_get_mac_binary factory 4)
+		lan_mac=$(macaddr_add "$wan_mac" 1)
+		;;
 	rt-n56u)
 		lan_mac=$(cat /sys/class/net/eth0/address)
 		lan_mac=$(macaddr_setbit_la "$lan_mac")