ALSA: ASoC: Add support for generic DAPM register modifier widget

This generic register modifier widget is for updating multiple codec
register bits at once when the widget changes its power state.

Signed-off-by: Jarkko Nikula <jarkko.nikula@nokia.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>