net/mlx5: Bridge, implement QinQ support

Implement support for new 802.1ad VLAN protocol type. Create new flow
groups that handle svlan tags. Create FDB flows with svlan tag match when
bridge VLAN is set to QinQ.

Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>