arm64: dts: mediatek: add missing cache properties

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

  mt7622-rfb1.dtb: l2-cache: 'cache-unified' is a required property
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230421223157.115367-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Matthias Brugger <matthias.bgg@gmail.com>

arch/arm64/boot/dts/mediatek/mt7622.dtsi

@@ -101,6 +101,7 @@ cpu1: cpu@1 {
 		L2: l2-cache {
 			compatible = "cache";
 			cache-level = <2>;
+			cache-unified;
 		};
 	};
 

arch/arm64/boot/dts/mediatek/mt8186.dtsi

@@ -258,6 +258,7 @@ l2_0: l2-cache0 {
 			cache-line-size = <64>;
 			cache-sets = <512>;
 			next-level-cache = <&l3_0>;
+			cache-unified;
 		};
 
 		l2_1: l2-cache1 {
@@ -267,6 +268,7 @@ l2_1: l2-cache1 {
 			cache-line-size = <64>;
 			cache-sets = <512>;
 			next-level-cache = <&l3_0>;
+			cache-unified;
 		};
 
 		l3_0: l3-cache {

arch/arm64/boot/dts/mediatek/mt8192.dtsi

@@ -228,6 +228,7 @@ l2_0: l2-cache0 {
 			cache-line-size = <64>;
 			cache-sets = <512>;
 			next-level-cache = <&l3_0>;
+			cache-unified;
 		};
 
 		l2_1: l2-cache1 {
@@ -237,6 +238,7 @@ l2_1: l2-cache1 {
 			cache-line-size = <64>;
 			cache-sets = <512>;
 			next-level-cache = <&l3_0>;
+			cache-unified;
 		};
 
 		l3_0: l3-cache {

arch/arm64/boot/dts/mediatek/mt8195.dtsi

@@ -285,6 +285,7 @@ l2_0: l2-cache0 {
 			cache-line-size = <64>;
 			cache-sets = <512>;
 			next-level-cache = <&l3_0>;
+			cache-unified;
 		};
 
 		l2_1: l2-cache1 {
@@ -294,6 +295,7 @@ l2_1: l2-cache1 {
 			cache-line-size = <64>;
 			cache-sets = <512>;
 			next-level-cache = <&l3_0>;
+			cache-unified;
 		};
 
 		l3_0: l3-cache {