ath79: ubnt-bullet-m-xw: Move eth0 mtd-mac-address to the common include

It's same for Bullet and Nanostation so far, so let's hope it's going to
be the same for other boards sharing the same platform.

Signed-off-by: Petr Štetiar <ynezz@true.cz>

target/linux/ath79/dts/ar9342_ubnt_bullet-m-xw.dts

@@ -24,8 +24,6 @@
 &eth0 {
 	status = "okay";
 
-	mtd-mac-address = <&eeprom 0x0>;
-
 	phy-mode = "rgmii";
 	phy-handle = <&phy4>;
 

target/linux/ath79/dts/ar9342_ubnt_xw.dtsi

@@ -117,3 +117,7 @@
 	mtd-cal-data = <&eeprom 0x1000>;
 	mtd-mac-address = <&eeprom 0x1002>;
 };
+
+&eth0 {
+	mtd-mac-address = <&eeprom 0x0>;
+};