wlcore/wl12xx/wl18xx: introduce quirk to remove TKIP header space

18xx chips do not require extra space in the TKIP header. Introduce a
new HW quirk to allow us to make this feature arch-specific. 12xx chip
will now have this quirk.

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>