dt-bindings: display: mediatek: dp: Reference common DAI properties

The MediaTek DP hardware supports audio and exposes a DAI, so the
'#sound-dai-cells' property is needed for describing the DAI links.

Reference the dai-common.yaml schema to allow '#sound-dai-cells' to be
used, and filter out non-DP compatibles as MediaTek eDP in the same
binding doesn't support audio.

This fixes dtbs_check error:
  '#sound-dai-cells' does not match any of the regexes: 'pinctrl-[0-9]+'

Signed-off-by: Fei Shao <fshao@chromium.org>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20241105090207.3892242-1-fshao@chromium.org/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

Documentation/devicetree/bindings/display/mediatek/mediatek,dp.yaml

@@ -42,6 +42,9 @@ properties:
   interrupts:
     maxItems: 1
 
+  '#sound-dai-cells':
+    const: 0
+
   ports:
     $ref: /schemas/graph.yaml#/properties/ports
     properties:
@@ -85,7 +88,21 @@ required:
   - ports
   - max-linkrate-mhz
 
-additionalProperties: false
+allOf:
+  - $ref: /schemas/sound/dai-common.yaml#
+  - if:
+      not:
+        properties:
+          compatible:
+            contains:
+              enum:
+                - mediatek,mt8188-dp-tx
+                - mediatek,mt8195-dp-tx
+    then:
+      properties:
+        '#sound-dai-cells': false
+
+unevaluatedProperties: false
 
 examples:
   - |