[ALSA] hda: Added mono_out_pin to autoconfig

Added a mono_out_pin field to autocfg struct, and code to parse
for the mono_out_line.

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