ALSA: hda - Apply asus-mode8 fixup to ASUS X71SL

Although the old quirk table showed ASUS X71SL with ALC663 codec being
compatible with asus-mode3 fixup, the bugzilla reporter explained that
asus-model8 fits better for the dual headphone controls.  So be it.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=191781


Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>