fm10k: fix memory leak

This was detected by Coverity.
The function skb_cow_head leaves skb alone on failure, so caller needs
to free.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/intel/fm10k/fm10k_netdev.c b/drivers/net/ethernet/intel/fm10k/fm10k_netdev.c
index 639263d..7781e80 100644
--- a/drivers/net/ethernet/intel/fm10k/fm10k_netdev.c
+++ b/drivers/net/ethernet/intel/fm10k/fm10k_netdev.c
@@ -627,8 +627,10 @@
 
 		/* verify the skb head is not shared */
 		err = skb_cow_head(skb, 0);
-		if (err)
+		if (err) {
+			dev_kfree_skb(skb);
 			return NETDEV_TX_OK;
+		}
 
 		/* locate vlan header */
 		vhdr = (struct vlan_hdr *)(skb->data + ETH_HLEN);