ramips: add label-mac-device for ELECOM WRC-GST devices

Update the dtsi for ELECOM WRC-1900GST and WRC-2533GST to add
label-mac-device alias.

Signed-off-by: INAGAKI Hiroshi <musashino.open@gmail.com>
[WRC-1900GST]
Acked-by: NOGUCHI Hiroshi <drvlabo@gmail.com>
[split patch, adjust commit title/message]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/ramips/dts/mt7621_elecom_wrc-gst.dtsi

@@ -11,6 +11,7 @@
 		led-failsafe = &led_power_green;
 		led-running = &led_power_green;
 		led-upgrade = &led_power_green;
+		label-mac-device = &wan;
 	};
 
 	chosen {
@@ -92,7 +93,7 @@
 
 &switch0 {
 	ports {
-		port@0 {
+		wan: port@0 {
 			status = "okay";
 			label = "wan";
 			mtd-mac-address = <&factory 0xe006>;