ramips: mt7621: add support for Netgear R6800

This patch adds support for the Netgear R6800, aka Netgear AC1900 and
R6800-100PES.

Specification:
- SoC: MediaTek MT7621AT (880 MHz)
- Flash: 128 MiB NAND
- RAM: 256 MiB
- Wireless: MediaTek MT7615EN b/g/n , MediaTek MT7615EN an+ac
- LAN speed: 10/100/1000
- LAN ports: 4
- WAN speed: 10/100/1000
- WAN ports: 1
- USB 2.0
- USB 3.0
- Serial baud rate of Bootloader and factory firmware: 57600

Known issues:
- Device has 3 wifi LEDs: Wifi 5Ghz, Wifi 2.4Ghz and Wifi on/off.
  Wifi on/off is not used.

Installation:
- apply factory image via stock web-gui.

Back to stock:
- nmrpflash can be used to recover to the stock Netgear firmware.

Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>

target/linux/ramips/mt7621/base-files/etc/board.d/01_leds

@@ -52,6 +52,13 @@ netgear,r6850|\
 netgear,wndr3700-v5)
 	ucidef_set_led_switch "wan" "wan" "$boardname:green:wan" "switch0" "0x10"
 	;;
+netgear,r6800)
+	ucidef_set_led_switch "wan" "WAN" "$boardname:white:wan" "switch0" "0x10"
+	ucidef_set_led_switch "lan1" "LAN1" "$boardname:white:lan1" "switch0" "0x08"
+	ucidef_set_led_switch "lan2" "LAN2" "$boardname:white:lan2" "switch0" "0x04"
+	ucidef_set_led_switch "lan3" "LAN3" "$boardname:white:lan3" "switch0" "0x02"
+	ucidef_set_led_switch "lan4" "LAN4" "$boardname:white:lan4" "switch0" "0x01"
+	;;
 tplink,re350-v1|\
 tplink,re650-v1)
 	ucidef_set_led_netdev "wifi2g" "Wifi 2.4G" "$boardname:blue:wifi2G" "wlan0"

target/linux/ramips/mt7621/base-files/etc/board.d/02_network

@@ -41,6 +41,7 @@ ramips_setup_interfaces()
 	netgear,r6220|\
 	netgear,r6260|\
 	netgear,r6350|\
+	netgear,r6800|\
 	netgear,r6850|\
 	netgear,wndr3700-v5|\
 	netis,wf2881|\
@@ -252,6 +253,7 @@ ramips_setup_macs()
 		;;
 	netgear,r6260|\
 	netgear,r6350|\
+	netgear,r6800|\
 	netgear,r6850)
 		wan_mac=$(macaddr_add "$(mtd_get_mac_binary factory 0x4)" 2)
 		;;

target/linux/ramips/mt7621/base-files/lib/upgrade/platform.sh

@@ -48,6 +48,7 @@ platform_do_upgrade() {
 	netgear,r6220|\
 	netgear,r6260|\
 	netgear,r6350|\
+	netgear,r6800|\
 	netgear,r6850|\
 	netis,wf2881|\
 	xiaomi,mir3g|\