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>