ASoC: rsnd: control DVC_DVUCR under rsnd_dvc_volume_update()

rsnd_dvc_volume_update() is main function to control
DVC feature like Digital Volume / Mute / Ramp etc.
DVC_DVUCR should be controlled under this function.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>