ALSA: hda/realtek - Enable the bass speaker of ASUS UX431FLC

ASUS reported that there's an bass speaker in addition to internal
speaker and it uses DAC 0x02. It was not enabled in the commit
436e2550 ("ALSA: hda/realtek - Enable internal speaker of ASUS
UX431FLC") which only enables the amplifier and the front speaker.
This commit enables the bass speaker on top of the aforementioned
work to improve the acoustic experience.

Fixes: 436e2550

 ("ALSA: hda/realtek - Enable internal speaker of ASUS UX431FLC")
Signed-off-by: Chris Chiu <chiu@endlessm.com>
Signed-off-by: Jian-Hong Pan <jian-hong@endlessm.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20191230031118.95076-1-chiu@endlessm.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>