net/mlx4_en: Explicitly set no vlan tags in WQE ctrl segment when no vlan is present

We do not set the ins_vlan field to zero when no vlan id is present in the packet.

Since WQEs in the TX ring are not zeroed out between uses, this oversight
could result in having vlan flags present in the WQE ctrl segment when no
vlan is preset.

Fixes: e38af4fa ('net/mlx4_en: Add support for hardware accelerated 802.1ad vlan')
Reported-by: Gideon Naim <gideonn@mellanox.com>
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>