[ALSA] hda-codec - Fix headphone auto-toggle on sigmatel codec

Fix/optimize the headphone auto-toggle function on sigmatel codecs.
The headphone pins are kept as output.  When headhpones are unplugged,
you cannot hear anyway ;)

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