arm64: dts: mediatek: Update mt81xx scpsys node to align with dt-bindings

Update scpsys nodes using simple-mfd in mt81xx SoC devicetree
to align with the bindings.

Add specific compatibles for syscon node, even it's a dummy compatible,
because syscon node must come with a specific compatible.

Remove the '#power-domain-cells" propertry since the simple-mfd node is
not the power domain provider; the provider is the child node.
Signed-off-by: Tinghan Shen <tinghan.shen@mediatek.com>
Link: https://lore.kernel.org/r/20220811025813.21492-8-tinghan.shen@mediatek.comSigned-off-by: Matthias Brugger <matthias.bgg@gmail.com>

arch/arm64/boot/dts/mediatek/mt8167.dtsi

@@ -36,9 +36,8 @@ apmixedsys: apmixedsys@10018000 {
 		};
 
 		scpsys: syscon@10006000 {
-			compatible = "syscon", "simple-mfd";
+			compatible = "mediatek,mt8167-scpsys", "syscon", "simple-mfd";
 			reg = <0 0x10006000 0 0x1000>;
-			#power-domain-cells = <1>;
 
 			spm: power-controller {
 				compatible = "mediatek,mt8167-power-controller";

arch/arm64/boot/dts/mediatek/mt8173.dtsi

@@ -444,9 +444,8 @@ pins1 {
 		};
 
 		scpsys: syscon@10006000 {
-			compatible = "syscon", "simple-mfd";
+			compatible = "mediatek,mt8173-scpsys", "syscon", "simple-mfd";
 			reg = <0 0x10006000 0 0x1000>;
-			#power-domain-cells = <1>;
 
 			/* System Power Manager */
 			spm: power-controller {

arch/arm64/boot/dts/mediatek/mt8183.dtsi

@@ -761,9 +761,8 @@ pio: pinctrl@10005000 {
 		};
 
 		scpsys: syscon@10006000 {
-			compatible = "syscon", "simple-mfd";
+			compatible = "mediatek,mt8183-scpsys", "syscon", "simple-mfd";
 			reg = <0 0x10006000 0 0x1000>;
-			#power-domain-cells = <1>;
 
 			/* System Power Manager */
 			spm: power-controller {

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

@@ -306,9 +306,8 @@ pio: pinctrl@10005000 {
 		};
 
 		scpsys: syscon@10006000 {
-			compatible = "syscon", "simple-mfd";
+			compatible = "mediatek,mt8192-scpsys", "syscon", "simple-mfd";
 			reg = <0 0x10006000 0 0x1000>;
-			#power-domain-cells = <1>;
 
 			/* System Power Manager */
 			spm: power-controller {