arm64: dts: lg: add missing cache properties

As all level 2 and level 3 caches are unified, add required
cache-unified and cache-level properties to fix warnings like:

  lg1312-ref.dtb: l2-cache0: 'cache-level' is a required property
Acked-by: Chanho Min <chanho.min@lge.com>
Link: https://lore.kernel.org/r/20230421223201.115439-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

arch/arm64/boot/dts/lg/lg1312.dtsi

@@ -48,6 +48,8 @@ cpu3: cpu@3 {
 		};
 		L2_0: l2-cache0 {
 			compatible = "cache";
+			cache-level = <2>;
+			cache-unified;
 		};
 	};
 

arch/arm64/boot/dts/lg/lg1313.dtsi

@@ -48,6 +48,8 @@ cpu3: cpu@3 {
 		};
 		L2_0: l2-cache0 {
 			compatible = "cache";
+			cache-level = <2>;
+			cache-unified;
 		};
 	};