iwlwifi: Don't unlock priv->mutex if it isn't locked

Commit b716bb91 ("iwlwifi: Cancel scanning upon association") moved the
test of priv->vif in iwl{3945,4964}_mac_config_interface() outside of
where priv->mutex is held, but still tries to do mutex_unlock() on
return.  This is clearly wrong and triggers a nasty lockdep warning when
this codepath is triggered.  Fix this by removing the mutex_unlock().
Signed-off-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl3945-base.c

@@ -6907,7 +6907,6 @@ static int iwl3945_mac_config_interface(struct ieee80211_hw *hw,
 
 	if (priv->vif != vif) {
 		IWL_DEBUG_MAC80211("leave - priv->vif != vif\n");
-		mutex_unlock(&priv->mutex);
 		return 0;
 	}
 

drivers/net/wireless/iwlwifi/iwl4965-base.c

@@ -6473,7 +6473,6 @@ static int iwl4965_mac_config_interface(struct ieee80211_hw *hw,
 
 	if (priv->vif != vif) {
 		IWL_DEBUG_MAC80211("leave - priv->vif != vif\n");
-		mutex_unlock(&priv->mutex);
 		return 0;
 	}