asus-nb-wmi: Add wapf4 quirk for the X550CC

As reported here: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1173681


the X550CC needs wapf=4 too.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>