[ALSA] ac97 - Fix VIA EPIA sound problem

Fix the bad sound quality on VIA EPIA system using VIA VT1617A
(ALSA bug#2381).

Signed-off-by: Andrey Liakhovets <liakh@dol.ru>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>