arm64: dts: renesas: r8a77990: Add I2C-DVFS device node

This patch adds I2C-DVFS device node for the R8A77990 SoC.

v2
* Drop aliases update as in upstream it is not required to configure the
  BD9571 PMIC for DDR backup, nor is the use of i2c are aliases desired.
* Do not describe the device as compatible with "renesas,rcar-gen3-iic" or
  "renesas,rmobile-iic" fallback compat strings. The absence of automatic
  transmission registers leads us to declare the r8a77990 IIC controller as
  incompatible.

v2.1
* Reduced register range to reflect documentation
Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
Signed-off-by: Yoshihiro Kaneko <ykaneko0929@gmail.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/r8a77990.dtsi

@@ -357,6 +357,20 @@ pfc: pin-controller@e6060000 {
 			reg = <0 0xe6060000 0 0x508>;
 		};
 
+		i2c_dvfs: i2c@e60b0000 {
+			#address-cells = <1>;
+			#size-cells = <0>;
+			compatible = "renesas,iic-r8a77990";
+			reg = <0 0xe60b0000 0 0x15>;
+			interrupts = <GIC_SPI 173 IRQ_TYPE_LEVEL_HIGH>;
+			clocks = <&cpg CPG_MOD 926>;
+			power-domains = <&sysc R8A77990_PD_ALWAYS_ON>;
+			resets = <&cpg 926>;
+			dmas = <&dmac0 0x11>, <&dmac0 0x10>;
+			dma-names = "tx", "rx";
+			status = "disabled";
+		};
+
 		cpg: clock-controller@e6150000 {
 			compatible = "renesas,r8a77990-cpg-mssr";
 			reg = <0 0xe6150000 0 0x1000>;