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

Fix dtschema validator warnings like:
    l2-cache-controller@48242000: $nodename:0:
        'l2-cache-controller@48242000' does not match '^(cache-controller|cpu)(@[0-9a-f,]+)*$'
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/boot/dts/omap4.dtsi

@@ -71,7 +71,7 @@ gic: interrupt-controller@48241000 {
 		interrupt-parent = <&gic>;
 	};
 
-	L2: l2-cache-controller@48242000 {
+	L2: cache-controller@48242000 {
 		compatible = "arm,pl310-cache";
 		reg = <0x48242000 0x1000>;
 		cache-unified;