ASoC: dt-bindings: audio-graph-port: add clocks on endpoint

Audio Graph endpoint is possible to have clocks, and system-clock-xxx,
but these are missing on audio-graph-port.yaml.
These have been already defined on simple-card.yaml.

This patch re-use these.  We will get below warning without this patch.

${LINUX}/arch/arm64/boot/dts/renesas/r8a77950-ulcb-kf.dtb: audio-codec@44: ports:port@0:endpoint: Unevaluated properties are not allowed ('clocks' was unexpected)
	From schema: ${LINUX}/Documentation/devicetree/bindings/sound/ti,pcm3168a.yaml

Link: https://lore.kernel.org/r/87pmcmpyml.wl-kuninori.morimoto.gx@renesas.comSigned-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87mt697rgg.wl-kuninori.morimoto.gx@renesas.comSigned-off-by: Mark Brown <broonie@kernel.org>

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

@@ -48,6 +48,15 @@ definitions:
         oneOf:
           - $ref: /schemas/types.yaml#/definitions/flag
           - $ref: /schemas/types.yaml#/definitions/phandle
+      clocks:
+        description: Indicates system clock
+        $ref: /schemas/types.yaml#/definitions/phandle
+      system-clock-frequency:
+        $ref: "simple-card.yaml#/definitions/system-clock-frequency"
+      system-clock-direction-out:
+        $ref: "simple-card.yaml#/definitions/system-clock-direction-out"
+      system-clock-fixed:
+        $ref: "simple-card.yaml#/definitions/system-clock-fixed"
 
       dai-format:
         description: audio format.