IB/mlx4: Enable RoCE v2 when the IB device is added

If the hardware supports RoCE v2, we configure the hardware UDP
port according to the RoCE v2 Annex when mlx4_ib device is added.

Signed-off-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>