mac80211: fix unbalanced locking in ieee80211_get_buffered_bc

This patch fixes unbalanced locking in ieee80211_get_buffered_bc

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 332ddcb..4214d03 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -2011,7 +2011,7 @@
 	}
 
 	if (WARN_ON(tx.skb != skb))
-		return NULL;
+		res = TX_DROP;
 
 	if (res == TX_DROP) {
 		I802_DEBUG_INC(local->tx_handlers_drop);