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: Nishant Sarmukadam <nishants@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/mwl8k.c b/drivers/net/wireless/mwl8k.c
index 9961765..5b5b9ec 100644
--- a/drivers/net/wireless/mwl8k.c
+++ b/drivers/net/wireless/mwl8k.c
@@ -2005,6 +2005,8 @@
 				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;
 		}