at91: dts: Unify naming of gpio-keys nodes

In DTS Checklist[1] we're now demanding proper generic node names, as
the name of a node should reflect the function of the device and use
generic name for that[2]. Everybody seems to be copy&pasting from DTS
files available in the repository today, so let's unify that naming
there as well and provide proper examples.

1. https://openwrt.org/submitting-patches#dts_checklist
2. https://github.com/devicetree-org/devicetree-specification/blob/master/source/devicetree-basics.rst#generic-names-recommendation

Signed-off-by: Petr Štetiar <ynezz@true.cz>
Signed-off-by: Christian Lamparter <chunkeey@gmail.com> [split up]

target/linux/at91/files/arch/arm/boot/dts/wb45n.dts

@@ -206,7 +206,7 @@
 		atheros,board-id = "SD32";
 	};
 
-	gpio_keys {
+	keys {
 		compatible = "gpio-keys";
 		#address-cells = <1>;
 		#size-cells = <0>;

target/linux/at91/files/arch/arm/boot/dts/wb50n.dts

@@ -73,7 +73,7 @@
 		};
 	};
 
-	gpio_keys {
+	keys {
 		compatible = "gpio-keys";
 		#address-cells = <1>;
 		#size-cells = <0>;