[ALSA] ac97 - Add virtual master control to VT1616/VT1617A codec.

Enable VMASTER for VT1616 / VT1617A codec.

Signed-off-by: Daniel Jacobowitz <dan@codesourcery.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>