dt-bindings: display: rockchip: document VOP gamma LUT address

Add the register specifier description for an
optional gamma LUT address.
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191010194351.17940-2-ezequiel@collabora.com

Documentation/devicetree/bindings/display/rockchip/rockchip-vop.txt

@@ -20,6 +20,10 @@ Required properties:
 		"rockchip,rk3228-vop";
 		"rockchip,rk3328-vop";
 
+- reg: Must contain one entry corresponding to the base address and length
+	of the register space. Can optionally contain a second entry
+	corresponding to the CRTC gamma LUT address.
+
 - interrupts: should contain a list of all VOP IP block interrupts in the
 		 order: VSYNC, LCD_SYSTEM. The interrupt specifier
 		 format depends on the interrupt controller used.
@@ -48,7 +52,7 @@ Example:
 SoC specific DT entry:
 	vopb: vopb@ff930000 {
 		compatible = "rockchip,rk3288-vop";
-		reg = <0xff930000 0x19c>;
+		reg = <0x0 0xff930000 0x0 0x19c>, <0x0 0xff931000 0x0 0x1000>;
 		interrupts = <GIC_SPI 15 IRQ_TYPE_LEVEL_HIGH>;
 		clocks = <&cru ACLK_VOP0>, <&cru DCLK_VOP0>, <&cru HCLK_VOP0>;
 		clock-names = "aclk_vop", "dclk_vop", "hclk_vop";