net/mlx5: E-switch, Create a second level FDB flow table

If firmware supports the forward action with a destination list
that includes a flow table, create a second level FDB flow table.

This is going to be used for flow based mirroring under the switchdev
offloads mode.

Signed-off-by: Chris Mi <chrism@mellanox.com>
Reviewed-by: Paul Blakey <paulb@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>