ASoC: codecs: Add support for the generic IIO auxiliary devices

Industrial I/O devices can be present in the audio path.
These devices needs to be used as audio components in order to be
fully integrated in the audio path.

This support allows to consider these Industrial I/O devices as
auxiliary audio devices and allows one to control them using mixer
controls.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://lore.kernel.org/r/20230623085830.749991-13-herve.codina@bootlin.com


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