net/mlx5: TX WQE update

Add new TX WQE fields for Connect-X5 vlan insertion support,
type and vlan_tci, when type = MLX5_ETH_WQE_INSERT_VLAN the
HW will insert the vlan and prio fields (vlan_tci) to the packet.

Those bits and the inline header fields are mutually exclusive, and
valid only when:
MLX5_CAP_ETH(mdev, wqe_inline_mode) == MLX5_CAP_INLINE_MODE_NOT_REQUIRED
and MLX5_CAP_ETH(mdev, wqe_vlan_insert),
who will be set in ConnectX-5 and later HW generations.

Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>