ASoC: dt-bindings: fsl,mqs: Document audio graph port

This device can be used in conjunction with audio-graph-card to provide
an endpoint for binding with the other side of the audio link.

Signed-off-by: Shengjiu Wang <[e-mail]>
Acked-by: "Rob Herring (Arm)" <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

Documentation/devicetree/bindings/sound/fsl,mqs.yaml

···
   resets:
     maxItems: 1
 
+  port:
+    $ref: audio-graph-port.yaml#
+    unevaluatedProperties: false
+
 required:
   - compatible
   - clocks