IB/mlx4: Enable device-managed steering support for IB ports too

Up until now, flow steering wasn't supported when using IB ports.

This patch enables support for flow steering if all hardware ports
support that, for example the new MLX4_DEV_CAP_FLAG2_DMFS_IPOIB mlx4
device capability.

Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>