[ALSA] hda-codec - Fix surround output on AD1986A

Fix surround output on AD1986A codec 3stack model.
The following bugs are fixed:
- init verbs for 3stack disabled the shared surround outputs
- a channel mode change resulted in the mute of surrounds

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>