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

Fix dtschema validator warnings like:
    l2-cache@fffff000: $nodename:0:
        'l2-cache@fffff000' does not match '^(cache-controller|cpu)(@[0-9a-f,]+)*$'

Fixes: 475dc86d08 ("arm: dts: socfpga: Add a base DTSI for Altera's Arria10 SOC")
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>

arch/arm/boot/dts/socfpga.dtsi

@@ -726,7 +726,7 @@
 			};
 		};
 
-		L2: l2-cache@fffef000 {
+		L2: cache-controller@fffef000 {
 			compatible = "arm,pl310-cache";
 			reg = <0xfffef000 0x1000>;
 			interrupts = <0 38 0x04>;

arch/arm/boot/dts/socfpga_arria10.dtsi

@@ -636,7 +636,7 @@
 			reg = <0xffcfb100 0x80>;
 		};
 
-		L2: l2-cache@fffff000 {
+		L2: cache-controller@fffff000 {
 			compatible = "arm,pl310-cache";
 			reg = <0xfffff000 0x1000>;
 			interrupts = <0 18 IRQ_TYPE_LEVEL_HIGH>;