[ALSA] soc - Fix power switching support for DAPM_SWITCH widgets

Signed-off-by: Milan plzik <milan.plzik@gmail.com>
Signed-off-by: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>