igb: Do not require CTRL.VME for tx VLAN tagging

While the datasheet of e1000e says it checks CTRL.VME for tx VLAN
tagging, igb's datasheet has no such statements. It also says for
"CTRL.VLE":
> This register only affects the VLAN Strip in Rx it does not have any
> influence in the Tx path in the 82576.
(Appendix A. Changes from the 82575)

There is no "CTRL.VLE" so it is more likely that it is a mistake of
CTRL.VME.

Fixes: fba7c3b ("igb: respect VMVIR and VMOLR for VLAN")
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Sriram Yagnaraman <sriram.yagnaraman@est.tech>
Signed-off-by: Jason Wang <jasowang@redhat.com>
(cherry picked from commit e209716)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

hw/net/igb_core.c

@@ -402,7 +402,7 @@ igb_tx_insert_vlan(IGBCore *core, uint16_t qn, struct igb_tx *tx,
         }
     }
 
-    if (insert_vlan && e1000x_vlan_enabled(core->mac)) {
+    if (insert_vlan) {
         net_tx_pkt_setup_vlan_header_ex(tx->tx_pkt, vlan,
             core->mac[VET] & 0xffff);
     }