mwl8k: Unmap the pci DMA address in xmit error path

We should unmap the DMA address in the error path, else it
causes resource leaks. Fix this.
Signed-off-by: NNishant Sarmukadam <nishants@marvell.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/mwl8k.c

@@ -2005,6 +2005,8 @@ mwl8k_txq_xmit(struct ieee80211_hw *hw,
 				spin_unlock(&priv->stream_lock);
 			}
 			spin_unlock_bh(&priv->tx_lock);
+			pci_unmap_single(priv->pdev, dma, skb->len,
+					 PCI_DMA_TODEVICE);
 			dev_kfree_skb(skb);
 			return;
 		}