ARM: dts: hisilicon: Align L2 cache-controller nodename with dtschema

Fix dtschema validator warnings like:
l2-cache: $nodename:0: 'l2-cache' does not match '^(cache-controller|cpu)(@[0-9a-f,]+)*$'

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Wei Xu <[e-mail]>

arch/arm/boot/dts/hi3620.dtsi

···
 		interrupt-parent = <&gic>;
 		ranges = <0 0xfc000000 0x2000000>;
 
-		L2: l2-cache {
+		L2: cache-controller {
 			compatible = "arm,pl310-cache";
 			reg = <0x100000 0x100000>;
 			interrupts = <0 15 4>;

arch/arm/boot/dts/hisi-x5hd2.dtsi

···
 			interrupts = <1 13 0xf01>;
 		};
 
-		l2: l2-cache {
+		l2: cache-controller {
 			compatible = "arm,pl310-cache";
 			reg = <0x00a10000 0x100000>;
 			interrupts = <0 15 4>;