ALSA: HDA: patch_analog: Quirk for Asus P5Q Premium/Pro boards.

Use 6STACK_DIG for the AD2000BX variant of the AD1989B chip used by Asus
on their Asus P5Q Premium and Pro boards.

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>