net/mlx5e: Add 802.1ad VLAN insertion support

Report VLAN insertion support for S-tagged packets and add support by
choosing the correct VLAN type in the WQE.

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