net/mlx5: Push devlink port PF/VF init/cleanup calls out of devlink_port_register/unregister()

In order to prepare for
mlx5_esw_offloads_devlink_port_register/unregister() to be used
for SFs as well, push out the PF/VF specific init/cleanup calls outside.
Introduce mlx5_eswitch_load/unload_pf_vf_vport() and call them from
there. Use these new helpers of PF/VF loading and make
mlx5_eswitch_local/unload_vport() reusable for SFs.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Shay Drory <shayd@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>