net/mlx5: Fix devlink controller number for ECVF

The controller number for ECVFs is always 0, because the ECPF must be
the eswitch owner for EC VFs to be enabled.

Fixes: dc131808

 ("net/mlx5: Enable devlink port for embedded cpu VF vports")
Signed-off-by: Daniel Jurgens <danielj@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>