oxnas: dts: Unify naming of gpio-led 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/oxnas/files/arch/arm/boot/dts/ox820-akitio-mycloud.dts

@@ -58,7 +58,7 @@
 		};
 	};
 
-	gpio-leds {
+	leds {
 		compatible = "gpio-leds";
 		pinctrl-names = "default";
 		pinctrl-0 = <&pinctrl_leds>;

target/linux/oxnas/files/arch/arm/boot/dts/ox820-mitrastar-stg212.dts

@@ -43,7 +43,7 @@
 		};
 	};
 
-	gpio-leds {
+	leds {
 		compatible = "gpio-leds";
 		status {
 			label = "zyxel:blue:status";

target/linux/oxnas/files/arch/arm/boot/dts/ox820-shuttle-kd20.dts

@@ -65,7 +65,7 @@
 		};
 	};
 
-	gpio-leds {
+	leds {
 		compatible = "gpio-leds";
 		status {
 			label = "kd20:blue:status";