arm64: dts: mediatek: mt6795: Fix issues in SCPSYS node

Add the "mediatek,mt6795-scpsys" compatible to the SCPSYS node
and remove #power-domain-cells (retaining it only in the power
controller subnode) to resolve dtbs_check warnings.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Author: AngeloGioacchino Del Regno

arch/arm64/boot/dts/mediatek/mt6795.dtsi

@@ -287,9 +287,8 @@
 		};
 
 		scpsys: syscon@10006000 {
-			compatible = "syscon", "simple-mfd";
+			compatible = "mediatek,mt6795-scpsys", "syscon", "simple-mfd";
 			reg = <0 0x10006000 0 0x1000>;
-			#power-domain-cells = <1>;
 
 			/* System Power Manager */
 			spm: power-controller {