IB/mlx5: Enable QP creation with cvlan offload

Enable creating a RAW Ethernet QP with cvlan stripping offload when
it's supported by the hardware.

Signed-off-by: Noa Osherovich <noaos@mellanox.com>
Reviewed-by: Maor Gottlieb <maorg@mellanox.com>
Reviewed-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>