ALSA: ac97: Add VT1613 AC97 codec support

Patch to add an VT1613 AC97 codec support.

This codec has additional DC offset removal control,
headphone output and no video input.

Signed-off-by: Maciej Szmigiero <mail@maciej.szmigiero.name>
Signed-off-by: Takashi Iwai <tiwai@suse.de>