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/871808Signed-off-by: NDavid Henningsson <david.henningsson@canonical.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>