ALSA: hda - Fix white noise on Asus UX501VW headset

For reducing the noise from the headset output on ASUS UX501VW,
call the existing fixup, alc_fixup_headset_mode_alc668(), additionally.

Thread: https://bbs.archlinux.org/viewtopic.php?id=209554



Signed-off-by: Kaho Ng <ngkaho1234@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>