net/mlx5: Fix unpublish devlink parameters

Cleanup routine missed to unpublish the parameters. Add it.

Fixes: e890acd5 ("net/mlx5: Add devlink flow_steering_mode parameter")
Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>