phy: rockchip-emmc: adapt binding to specifiy register offset and length

The emmc-phy occupies a contiguous set of 8 registers inside the general
register files, so the reg property should specify this.
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>

Documentation/devicetree/bindings/phy/rockchip-emmc-phy.txt

@@ -4,7 +4,7 @@ Rockchip EMMC PHY
 Required properties:
  - compatible: rockchip,rk3399-emmc-phy
  - #phy-cells: must be 0
- - reg: PHY configure reg address offset in "general
+ - reg: PHY register address offset and length in "general
    register files"
 
 Example:
@@ -12,12 +12,14 @@ Example:
 
 grf: syscon@ff770000 {
 	compatible = "rockchip,rk3399-grf", "syscon", "simple-mfd";
+	#address-cells = <1>;
+	#size-cells = <1>;
 
 ...
 
 	emmcphy: phy@f780 {
 		compatible = "rockchip,rk3399-emmc-phy";
-		reg = <0xf780>;
+		reg = <0xf780 0x20>;
 		#phy-cells = <0>;
 	};
 };