ASoC: ak4118: Add support for AK4118 S/PDIF transceiver

The AK4118A is a digital audio transceiver supporting 8 input channels
at 192kHz and with 24bits resolution.
It converts the S/PDIF signal to I2S format and is configurable over I2C.

This driver introduce a minimal support of the AK4118, like selecting the
input channel, reading input frequency and detecting some errors.

Datasheet is available here:
https://www.akm.com/akm/en/file/datasheet/AK4118AEQ.pdf



Signed-off-by: Adrien Charruel <adrien.charruel@devialet.com>
Signed-off-by: Clément Péron <peron.clem@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>