It seems that a workaround for Thinkpad T440s crackling noise can be
applied generically to all Thinkpad models: namely, disabling the
default alc269 shutup callback.  This patch moves it to the existing
alc_fixup_tpt440_dock() while also replacing the rest code with
another existing alc_fixup_disable_aamix().  It resulted in a good
code reduction.

Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=958439Reported-and-tested-by: Benjamin Poirier <bpoirier@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>