ASoC: Replace remaining use of *_volsw_2r with *_volsw

The snd_soc_*_volsw_2r functionality has been merged to
*volsw callbacks.
Few places still used the get, or put variant of volsw_2r,
replace those with the corresponding *_volsw.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>