dt-bindings: mfd: mediatek: Add codec property for MT6357 PMIC

Add the audio codec sub-device. This sub-device is used to set the
optional voltage values according to the hardware.
The properties are:
  - Setup of microphone bias voltage.
  - Setup of the speaker pin pull-down.

Also, add the audio power supply property which is dedicated for
the audio codec sub-device.

Signed-off-by: Alexandre Mergnat <amergnat@baylibre.com>
Link: https://patch.msgid.link/20240226-audio-i350-v7-3-6518d953a141@baylibre.com


Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>