ALSA: hda - Mute headphone pin on suspend on XPS13 9333

Muting the headphone output pin right before the codec suspension
prevents pop noises when headphones are plugged in (except for a
barely audible click noise).
This solution allows to truly save some power when headphones are
plugged in unlike the previous solution (033b0a7c:
"ALSA: hda - Pop noises fix for XPS13 9333")

Signed-off-by: Gabriele Mazzotta <gabriele.mzt@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>