dt-bindings: display: Use OF graph schema

Now that we have a graph schema, rework the display related schemas to use
it. Mostly this is adding a reference to graph.yaml and dropping duplicate
parts from schemas.

In panel-common.yaml, 'ports' is dropped. Any binding using 'ports'
should be one with more than 1 port node, and the binding must define
what each port is.

Note that ti,sn65dsi86.yaml, ti,tfp410,yaml and toshiba,tc358768.yaml will
need further updates to use video-interfaces.yaml once that lands.

Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210104180724.2275098-1-robh@kernel.org

Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml

@@ -45,25 +45,17 @@ properties:
           - thine,thc63lvdm83d # For the THC63LVDM83D LVDS serializer
 
   ports:
-    type: object
-    description: |
-      This device has two video ports. Their connections are modeled using the
-      OF graph bindings specified in Documentation/devicetree/bindings/graph.txt
+    $ref: /schemas/graph.yaml#/properties/ports
+
     properties:
-      '#address-cells':
-        const: 1
-
-      '#size-cells':
-        const: 0
-
       port@0:
-        type: object
+        $ref: /schemas/graph.yaml#/properties/port
         description: |
           For LVDS encoders, port 0 is the parallel input
           For LVDS decoders, port 0 is the LVDS input
 
       port@1:
-        type: object
+        $ref: /schemas/graph.yaml#/properties/port
         description: |
           For LVDS encoders, port 1 is the LVDS output
           For LVDS decoders, port 1 is the parallel output
@@ -72,8 +64,6 @@ properties:
       - port@0
       - port@1
 
-    additionalProperties: false
-
   powerdown-gpios:
     description:
       The GPIO used to control the power down line of this device.