ALSA: hda - Minor update for alc662-parser functions

Allow alc662_dac_to_mix() and alc662_look_for_dac() to parse
down the selector widget that is found in ALC880-type codecs,
and rename them to alc_auto_*() accordingly.
This is for the next coming multi-io extensions.

Signed-off-by: Takashi Iwai <tiwai@suse.de>