Fix the auto-mute controls of ALC880 uniwill model.  Split to two
individual functions to handle HP and front-mic mutes.  For front-mic
mute, use snd_hda_codec_amp_update() to be consistent with mixer.
Signed-off-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NJaroslav Kysela <perex@suse.cz>