ALSA: hda - Rename ASUS subwoofer quirks

Just a small refactoring to make the next patch slightly simpler.

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
ALSA: hda - Add subwoofer quirks for Asus UX51VZH and N55SF

Bug reporter report that the -mode4 makes the subwoofer work.
I have simplified the quirk a bit to avoid possible regressions
with the microphones.

BugLink: https://bugs.launchpad.net/bugs/871808
Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>