ASoC: dt-bindings: audio-graph-port: remove prefix

Audio Graph port doesn't use prefix.
This patch removes it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/87lelt7rg6.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/audio-graph-port.yaml

@@ -15,9 +15,6 @@ definitions:
   port-base:
     $ref: /schemas/graph.yaml#/$defs/port-base
     properties:
-      prefix:
-        description: "device name prefix"
-        $ref: /schemas/types.yaml#/definitions/string
       convert-rate:
         $ref: "/schemas/sound/dai-params.yaml#/$defs/dai-sample-rate"
       convert-channels: