IB/mlx4: Add support for steerable IB UD QPs

This patch adds support for steerable (NETIF) QP creation.  When we
create the device, we allocate a range of steerable QPs.

Afterward when a QP is created with the NETIF flag, it's allocated
from this range.  Allocation is managed by bitmap allocator.

Internal steering rules for those QPs is automatically generated on
their creation.

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