cfg80211: Handle WMM rules in regulatory domain intersection

The support added for regulatory WMM rules did not handle
the case of regulatory domain intersections. Fix it.

Signed-off-by: Ilan Peer <ilan.peer@intel.com>
Fixes: 230ebaa1

 ("cfg80211: read wmm rules from regulatory database")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>