ARM: dts: rockchip: add io-domains node to rk3188.dtsi

The compatible string below was added to
rockchip-io-domain.txt, but never added to the device tree,
so add a io-domains node to rk3188.dtsi

"rockchip,rk3188-io-voltage-domain"

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Link: https://lore.kernel.org/r/20210625111746.6269-3-jbx6244@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

Author: Johan Jonker

arch/arm/boot/dts/rk3188.dtsi

@@ -641,6 +641,11 @@
 &grf {
 	compatible = "rockchip,rk3188-grf", "syscon", "simple-mfd";
 
+	io_domains: io-domains {
+		compatible = "rockchip,rk3188-io-voltage-domain";
+		status = "disabled";
+	};
+
 	usbphy: usbphy {
 		compatible = "rockchip,rk3188-usb-phy",
 			     "rockchip,rk3288-usb-phy";