net/mlx5: Add IFC bits needed for single FDB mode

Currently we operate in a mode where each eswitch manager has a separate
FDB. In order to combine these multiple FDBs we expose new caps to allow
this:

- Set root flow table which isn't native.
- Set FDB a different selection mode when in LAG mode.

Signed-off-by: Mark Bloch <mbloch@nvidia.com>
Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>