dt-bindings: display: convert innolux,p079zca to DT Schema

As the binding matches panel-simple-dsi, added the compatible to the
panel-simple-dsi list.
With this change enable-gpios is now optional.

v2:
  - It is a DSI panel, add it to panel-simple-dsi (Rob)
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Chris Zhong <zyw@rock-chips.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200704102806.735713-2-sam@ravnborg.org

Documentation/devicetree/bindings/display/panel/innolux,p079zca.txt

-Innolux P079ZCA 7.85" 768x1024 TFT LCD panel
-
-Required properties:
-- compatible: should be "innolux,p079zca"
-- reg: DSI virtual channel of the peripheral
-- power-supply: phandle of the regulator that provides the supply voltage
-- enable-gpios: panel enable gpio
-
-Optional properties:
-- backlight: phandle of the backlight device attached to the panel
-
-Example:
-
-	&mipi_dsi {
-		panel@0 {
-			compatible = "innolux,p079zca";
-			reg = <0>;
-			power-supply = <...>;
-			backlight = <&backlight>;
-			enable-gpios = <&gpio1 13 GPIO_ACTIVE_HIGH>;
-		};
-	};

Documentation/devicetree/bindings/display/panel/panel-simple-dsi.yaml

@@ -33,6 +33,8 @@ properties:
       - auo,b080uan01
         # Boe Corporation 8.0" WUXGA TFT LCD panel
       - boe,tv080wum-nl0
+        # Innolux P079ZCA 7.85" 768x1024 TFT LCD panel
+      - innolux,p079zca
         # Kingdisplay KD097D04 9.7" 1536x2048 TFT LCD panel
       - kingdisplay,kd097d04
         # LG ACX467AKM-7 4.95" 1080×1920 LCD Panel