ath79: fritz300e: awk-1137c: remove label-mac-device

This is already done in userspace. In addition, it's hard to do in nvmem
as they rely on non standard locations.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/21035
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

target/linux/ath79/dts/ar7242_avm_fritz300e.dts

@@ -15,7 +15,6 @@
 		led-failsafe = &led_power;
 		led-running = &led_power;
 		led-upgrade = &led_power;
-		label-mac-device = &ath9k;
 	};
 
 	keys {

target/linux/ath79/dts/ar9344_moxa_awk-1137c.dts

@@ -15,7 +15,6 @@
 		led-failsafe = &led_status_red;
 		led-running = &led_status_green;
 		led-upgrade = &led_status_red;
-		label-mac-device = &eth1;
 	};
 
 	keys {