ARM: dts: rockchip: Add io-domain node for rk3228

This patch adds io-domain support for rk3228 SoC.
Signed-off-by: David Wu <david.wu@rock-chips.com>
Signed-off-by: Frank Wang <frank.wang@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm/boot/dts/rk322x.dtsi

@@ -228,6 +228,11 @@ grf: syscon@11000000 {
 		#address-cells = <1>;
 		#size-cells = <1>;
 
+		io_domains: io-domains {
+			compatible = "rockchip,rk3228-io-voltage-domain";
+			status = "disabled";
+		};
+
 		u2phy0: usb2-phy@760 {
 			compatible = "rockchip,rk3228-usb2phy";
 			reg = <0x0760 0x0c>;