ibmvnic: fix accelerated VLAN handling

Don't request tag insertion when it isn't present in outgoing skb.
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ibm/ibmvnic.c

@@ -1545,7 +1545,7 @@ static netdev_tx_t ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 	tx_crq.v1.sge_len = cpu_to_be32(skb->len);
 	tx_crq.v1.ioba = cpu_to_be64(data_dma_addr);
 
-	if (adapter->vlan_header_insertion) {
+	if (adapter->vlan_header_insertion && skb_vlan_tag_present(skb)) {
 		tx_crq.v1.flags2 |= IBMVNIC_TX_VLAN_INSERT;
 		tx_crq.v1.vlan_id = cpu_to_be16(skb->vlan_tci);
 	}