ASoC: da732x: Mark DC offset control registers volatile

ASoC: da732x: Mark DC offset control registers volatile

commit 75306820248e26d15d84acf4e297b9fb27dd3bb2 upstream.

The driver reads from the DC offset control registers during callibration
but since the registers are marked as volatile and there is a register
cache the values will not be read from the hardware after the first reading
rendering the callibration ineffective.

It appears that the driver was originally written for the ASoC level
register I/O code but converted to regmap prior to merge and this issue
was missed during the conversion as the framework level volatile register
functionality was not being used.

Signed-off-by: Mark Brown <broonie@linaro.org>
Acked-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>