ASoC: core: Combine snd_soc_put_volsw/put_volsw_2r functions

Handle the put_volsw/put_volsw_2r in one function.

To avoid build breakage in twl6040 keep the
snd_soc_put_volsw_2r as define, and map it snd_soc_put_volsw.

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