arm64: dts: renesas: r8a77970: add MMC support

Define the generic R8A77970 part of the MMC0 (SDHI2) device node.

Based on the original (and large) patches by Vladimir Barinov.
Signed-off-by: Vladimir Barinov <vladimir.barinov@cogentembedded.com>
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/r8a77970.dtsi

@@ -754,6 +754,18 @@ ipmmu_vi0: mmu@febd0000 {
 			#iommu-cells = <1>;
 		};
 
+		mmc0: mmc@ee140000 {
+			compatible = "renesas,sdhi-r8a77970",
+				     "renesas,rcar-gen3-sdhi";
+			reg = <0 0xee140000 0 0x2000>;
+			interrupts = <GIC_SPI 165 IRQ_TYPE_LEVEL_HIGH>;
+			clocks = <&cpg CPG_MOD 314>;
+			power-domains = <&sysc R8A77970_PD_ALWAYS_ON>;
+			resets = <&cpg 314>;
+			max-frequency = <200000000>;
+			status = "disabled";
+		};
+
 		gic: interrupt-controller@f1010000 {
 			compatible = "arm,gic-400";
 			#interrupt-cells = <3>;