ALSA: hda: VREF powerdown for headphones

Add support for powering down VREF on standard headphone insertion, also
powers up the VREF on a headset insertion.

Signed-off-by: Matthew Ranostay <mranostay@embeddedalley.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>