ASoC: dt-bindings: marvell, mmp-sspa: Use audio-graph-port schema

Now that we have a graph schema, reference it from the marvell,mmp-sspa
schema.

Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Lubomir Rintel <lkundrak@v3.sk>
Link: https://lore.kernel.org/r/20201117013349.2458416-4-robh@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/marvell,mmp-sspa.yaml

@@ -9,6 +9,9 @@ title: Marvel SSPA Digital Audio Interface Bindings
 maintainers:
   - Lubomir Rintel <lkundrak@v3.sk>
 
+allOf:
+  - $ref: audio-graph-port.yaml#
+
 properties:
   $nodename:
     pattern: "^audio-controller(@.*)?$"
@@ -58,29 +61,9 @@ properties:
         type: object
 
         properties:
-          remote-endpoint: true
-
-          frame-master:
-            type: boolean
-            description: SoC generates the frame clock
-
-          bitclock-master:
-            type: boolean
-            description: SoC generates the bit clock
-
           dai-format:
-            $ref: /schemas/types.yaml#/definitions/string
-            description: The digital audio format
             const: i2s
 
-        required:
-          - remote-endpoint
-
-    required:
-      - endpoint
-
-    additionalProperties: false
-
 required:
   - "#sound-dai-cells"
   - compatible
@@ -112,8 +95,6 @@ examples:
       port {
         endpoint {
           remote-endpoint = <&rt5631_0>;
-          frame-master;
-          bitclock-master;
           dai-format = "i2s";
         };
       };