ARM: dts: ste: 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 <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200626080552.3627-1-krzk@kernel.orgSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

arch/arm/boot/dts/ste-dbx5x0.dtsi

@@ -260,7 +260,7 @@ backupram@80150000 {
 			reg = <0x80150000 0x2000>;
 		};
 
-		L2: l2-cache {
+		L2: cache-controller {
 			compatible = "arm,pl310-cache";
 			reg = <0xa0412000 0x1000>;
 			interrupts = <GIC_SPI 13 IRQ_TYPE_LEVEL_HIGH>;

arch/arm/boot/dts/ste-nomadik-stn8815.dtsi

@@ -15,7 +15,7 @@ memory {
 		    <0x08000000 0x04000000>;
 	};
 
-	L2: l2-cache {
+	L2: cache-controller {
 		compatible = "arm,l210-cache";
 		reg = <0x10210000 0x1000>;
 		interrupt-parent = <&vica>;