ARM: dts: armada-370-xp: Remove button address and fixup names

The gpio-key nodes do not have a reg property, so remove the address from
the unit name.

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>

arch/arm/boot/dts/armada-xp-openblocks-ax3-4.dts

@@ -139,7 +139,7 @@
 				#address-cells = <1>;
 				#size-cells = <0>;
 
-				button@1 {
+				init {
 					label = "Init Button";
 					linux,code = <KEY_POWER>;
 					gpios = <&gpio1 28 GPIO_ACTIVE_HIGH>;