mlx5/core: E-Switch, Allocate ECPF vport if it's an eswitch manager

Eswitch vport is needed for eswitch manager when creating LAG,
to create egress rules. However, this was not handled when ECPF is
an eswitch manager.

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