ASoC: sgtl5000: add ADC mute control

This control mute/unmute the ADC input of SGTL5000
using its CHIP_ANA_CTRL register.

Signed-off-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
Reviewed-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Igor Opaniuk <igor.opaniuk@toradex.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20190719100524.23300-5-oleksandr.suvorov@toradex.com


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