mac80211: reject setting masked mac addresses

If a driver registers an address mask we should ensure that no
interface gets an address assigned that isn't covered by the
registered address mask. This prevents invalid configurations
from reaching the device and causing problems.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
[change function flow to reduce indentation, fix locking]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>