ASoC: dt-bindings: update fsl-asoc-card bindings after imx-spdif merge

ASoC: dt-bindings: update fsl-asoc-card bindings after imx-spdif merge

The S/PDIF audio card support with compatible "fsl,imx-audio-spdif"
was merged from imx-spdif into the fsl-asoc-card driver.
It makes possible to use an S/PDIF with an ASRC.

This merge introduces new DT bindings to use with compatible
"fsl,imx-audio-spdif" to follow the way fsl-asoc-card works:
* the "spdif-controller" property from imx-spdif is named "audio-cpu"
  in fsl-asoc-card.
* fsl-asoc-card uses codecs explicitly declared in DT
  with "audio-codec".
  With an SPDIF, codec drivers spdif_transmitter and
  spdif_receiver should be used.
  Driver imx-spdif used instead the dummy codec and a pair of
  boolean properties, "spdif-in" and "spdif-out".

In an upcoming commit, in-tree DTs will be modified to follow these new
properties:
* Property "spdif-controller" will be renamed "audio-cpu".
* spdif_transmitter and spdif_receiver nodes will be declared
  and linked to the fsl-asoc-card node with the property "audio-codec".

To keep backward compatibility with other DTs, support for
"spdif-controller", "spdif-in" and "spdif-out" properties is kept.
However, it is recommended to use the new properties if possible.
It is better to declare transmitter and/or receiver
in DT than using the dummy codec.

DTs using compatible "fsl,imx-audio-spdif" are still supported, and
fsl-asoc-card will behave the same as imx-spdif for these DTs.

Signed-off-by: Elinor Montmasson <elinor.montmasson@savoirfairelinux.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20240627083104.123357-6-elinor.montmasson@savoirfairelinux.com
Signed-off-by: Mark Brown <broonie@kernel.org>