[ALSA] hda: Enable SPDIF in/out on some stac9205 boards

Added support for some boards with SPDIF in/out, and cleaned up the GPIO
enable function.

Signed-off-by: Matthew Ranostay <mranostay@embeddedalley.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>