net/mlx5: Use devlink port pointer to get the pointer of container SF struct

Benefit from the fact that struct devlink_port is eventually embedded
in struct mlx5_sf and use container_of() macro to get it instead of the
xarray lookup in every devlink port op.

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