ARM: dts: spear: 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]>
Acked-by: Viresh Kumar <[e-mail]>

arch/arm/boot/dts/spear13xx.dtsi

···
 			      0 7 0x04>;
 	};
 
-	L2: l2-cache {
+	L2: cache-controller {
 		    compatible = "arm,pl310-cache";
 		    reg = <0xed000000 0x1000>;
 		    cache-unified;