ASoC: bindings: fsl-asoc-card: Add mclk-id optional property

Support setting the sound card main clock input from the device-tree
using the mclk-id property.

Signed-off-by: Ariel D'Alessandro <ariel.dalessandro@collabora.com>
Link: https://lore.kernel.org/r/20220117132109.283365-4-ariel.dalessandro@collabora.com


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