ALSA: hda/sigmatel - Disable automute for Elo VuPoint

The Elo VuPoint 15MX has two headphone jacks of which neither work by
default. Disabling automute allows ALSA to work normally with the
speakers & left headphone jack.

Future pin configuration changes may be required in the future to get
the right headphone jack working in tandem.

Signed-off-by: Michael Pobega <mpobega@neverware.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>