octeon: add support for Ubiquiti UniFi Security Gateway

Ubiquiti UniFi Security Gateway (USG) is largely identical to
the EdgeRouter Lite (ERLite-3) apart from a different board ID
and two dome leds.

Device data (from WikiDev):
  CPU: Cavium Octeon Plus CN5020 @500MHz 2-cores
  Ethernet: 3x Atheros AR8035-A GbE PHY's
  Flash: On-board 4MB Flash
  Storage: Internal 3.8GB USB Flash (Kingston ID) drive
    w/ 1.5GB free for use occupies single internal USB port.
  Serial: 1x RJ45 port on front panel. 115200, 8N1
  Buttons: 1x Reset

Flash instructions are identical to EdgeRouter Lite.

Signed-off-by: Clemens Hopfer <openwrt@wireloss.net>

target/linux/octeon/base-files/lib/preinit/01_sysinfo

@@ -17,7 +17,8 @@ do_sysinfo_octeon() {
 		name="erpro"
 		;;
 
-	"UBNT_E300"*)
+	"UBNT_E300"*|\
+	"UBNT_USG"*)
 		# let generic 02_sysinfo handle it since device has its own device tree
 		return 0
 		;;

target/linux/octeon/base-files/lib/preinit/79_move_config

@@ -15,7 +15,8 @@ octeon_move_config() {
 	. /lib/functions.sh
 
 	case "$(board_name)" in
-		erlite)
+		erlite|\
+		ubnt,usg)
 			move_config "/dev/sda1"
 			;;
 		itus,shield-router)