wifi: cfg80211: fix locking in regulatory disconnect

commit f7e60032 upstream.

This should use wiphy_lock() now instead of requiring the
RTNL, since __cfg80211_leave() via cfg80211_leave() is now
requiring that lock to be held.

Fixes: a05829a7

 ("cfg80211: avoid holding the RTNL when calling the driver")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>