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

Fix dtschema validator warnings like:
l2-cache@2040000: $nodename:0:
'l2-cache@2040000' does not match '^(cache-controller|cpu)(@[0-9a-f,]+)*$'

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

arch/arm/boot/dts/qcom-mdm9615.dtsi

···
 		ranges;
 		compatible = "simple-bus";
 
-		L2: l2-cache@2040000 {
+		L2: cache-controller@2040000 {
 			compatible = "arm,pl310-cache";
 			reg = <0x02040000 0x1000>;
 			arm,data-latency = <2 2 0>;