When plugging a headphone or headset, lots of noise is heard from
internal speaker, after changing the automute via amp instead of
pinctl, the noise disappears.

BugLink: https://bugs.launchpad.net/bugs/1268468
Cc: David Henningsson <david.henningsson@canonical.com>
Cc: stable@vger.kernel.org
Signed-off-by: Hui Wang <hui.wang@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>