cfg80211: export interface stopping function

This exports a new cfg80211_stop_iface() function.

This is intended for driver internal interface
combination management and channel switching.

Due to locking issues (it re-enters driver) the
call is asynchronous and uses cfg80211 event
list/worker.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/wireless/util.c b/net/wireless/util.c
index 7c47fa0..a756429 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -839,6 +839,9 @@
 			__cfg80211_ibss_joined(wdev->netdev, ev->ij.bssid,
 					       ev->ij.channel);
 			break;
+		case EVENT_STOPPED:
+			__cfg80211_leave(wiphy_to_rdev(wdev->wiphy), wdev);
+			break;
 		}
 		wdev_unlock(wdev);