ARM: dts: alpine: Align GIC nodename with dtschema

Fix dtschema validator warnings like:
    gic@fb001000: $nodename:0:
        'gic@fb001000' does not match '^interrupt-controller(@[0-9a-f,]+)*$'

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>

arch/arm/boot/dts/alpine.dtsi

@@ -91,7 +91,7 @@
 		};
 
 		/* Interrupt Controller */
-		gic: gic@fb001000 {
+		gic: interrupt-controller@fb001000 {
 			compatible = "arm,cortex-a15-gic";
 			#interrupt-cells = <3>;
 			#size-cells = <0>;