sunvnet: fix a memory leak in vnet_handle_offloads

when skb_gso_segment returns error, the original skb should be freed

Signed-off-by: Li RongQing <roy.qing.li@gmail.com>
Acked-by: David L Stevens <david.stevens@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>