ASoC: dt-bindings: fsl,imx-asrc: 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 <shengjiu.wang@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: "Rob Herring (Arm)" <robh@kernel.org>
Link: https://patch.msgid.link/20250306053138.1914956-1-shengjiu.wang@nxp.com


Signed-off-by: Mark Brown <broonie@kernel.org>