ALSA: hda - Fix subwoofer pin on ASUS N751 and N551

ALSA: hda - Fix subwoofer pin on ASUS N751 and N551

Subwoofer does not work out of the box on ASUS N751/N551 laptops. This
patch fixes it. Patch tested on N751 laptop. N551 part is not tested,
but according to [1] and [2] this laptop requires similar changes, so I
included them in the patch.

1. https://github.com/honsiorovskyi/asus-n551-hda-fix
2. https://bugs.launchpad.net/ubuntu/+source/alsa-tools/+bug/1405691

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=117781
Signed-off-by: Yura Pakhuchiy <pakhuchiy@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>