asus-nb-wmi: Add wapf=4 quirk for X456UA/X456UF

These laptops boot with wifi as hard-blocked, with no obvious way to
enable it. Using a quirk to set wapf=4 solves the problem.

Signed-off-by: Daniel Drake <drake@endlessm.com>
Acked-by: Corentin Chary <corentin.chary@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>