net/mlx5: Call mlx5_sf_id_erase() once in mlx5_sf_dealloc()

Before every call of mlx5_sf_dealloc(), there is a call to
mlx5_sf_id_erase(). So move it to the beginning of mlx5_sf_dealloc().
Also remove redundant mlx5_sf_id_erase() call from mlx5_sf_free()
as it is called only from mlx5_sf_dealloc().

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