ath5k: fix recursive locking in ath5k_beacon_update

ath5k_beacon_update takes sc->lock upon entry.  However, it is only
called from within ath5k_config_interface, which already holds the lock.
Remove the unnecessary locking from ath5k_beacon_update.

Signed-off-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath5k/base.c

@@ -3065,8 +3065,6 @@ ath5k_beacon_update(struct ieee80211_hw *hw, struct sk_buff *skb)
 
 	ath5k_debug_dump_skb(sc, skb, "BC  ", 1);
 
-	mutex_lock(&sc->lock);
-
 	if (sc->opmode != IEEE80211_IF_TYPE_IBSS) {
 		ret = -EIO;
 		goto end;
@@ -3083,7 +3081,6 @@ ath5k_beacon_update(struct ieee80211_hw *hw, struct sk_buff *skb)
 	}
 
 end:
-	mutex_unlock(&sc->lock);
 	return ret;
 }