ath9k: unlock on error path in ath9k_change_interface()

There is a missing unlock when we hit the "No beacon slot available"
error condition.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/main.c

@@ -1456,6 +1456,7 @@ static int ath9k_change_interface(struct ieee80211_hw *hw,
 	struct ath_wiphy *aphy = hw->priv;
 	struct ath_softc *sc = aphy->sc;
 	struct ath_common *common = ath9k_hw_common(sc->sc_ah);
+	int ret = 0;
 
 	ath_dbg(common, ATH_DBG_CONFIG, "Change Interface\n");
 	mutex_lock(&sc->mutex);
@@ -1465,7 +1466,8 @@ static int ath9k_change_interface(struct ieee80211_hw *hw,
 	case NL80211_IFTYPE_ADHOC:
 		if (sc->nbcnvifs >= ATH_BCBUF) {
 			ath_err(common, "No beacon slot available\n");
-			return -ENOBUFS;
+			ret = -ENOBUFS;
+			goto out;
 		}
 		break;
 	case NL80211_IFTYPE_STATION:
@@ -1479,14 +1481,15 @@ static int ath9k_change_interface(struct ieee80211_hw *hw,
 	default:
 		ath_err(common, "Interface type %d not yet supported\n",
 				vif->type);
-		mutex_unlock(&sc->mutex);
-		return -ENOTSUPP;
+		ret = -ENOTSUPP;
+		goto out;
 	}
 	vif->type = new_type;
 	vif->p2p = p2p;
 
+out:
 	mutex_unlock(&sc->mutex);
-	return 0;
+	return ret;
 }
 
 static void ath9k_remove_interface(struct ieee80211_hw *hw,