mac80211: fix tim_lock locking

The ieee80211_beacon_add_tim() function might be called
by drivers with BHs enabled, which causes a potential
deadlock if TX happens at the same time and attempts to
lock the tim_lock as well. Use spin_lock_bh to fix it.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/tx.c

@@ -2360,9 +2360,9 @@ static int ieee80211_beacon_add_tim(struct ieee80211_sub_if_data *sdata,
 	if (local->tim_in_locked_section) {
 		__ieee80211_beacon_add_tim(sdata, ps, skb);
 	} else {
-		spin_lock(&local->tim_lock);
+		spin_lock_bh(&local->tim_lock);
 		__ieee80211_beacon_add_tim(sdata, ps, skb);
-		spin_unlock(&local->tim_lock);
+		spin_unlock_bh(&local->tim_lock);
 	}
 
 	return 0;