ALSA: hda - Fix noise on Gigabyte Z170X mobo

Gigabyte Z710X mobo with ALC1150 codec gets significant noises from
the analog loopback routes even if their inputs are all muted.
Simply kill the aamix for fixing it.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=108301
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>