IB/core: Add flow steering support for IPoIB UD traffic

When creating an IPoIB UD QP, provide a hint to the low level driver
that the QP should support flow-steering.  This means that privileged
user space applications can steer TCP/IP IPoIB traffic from the
network stack, in a similar manner done with Ethernet RAW_PACKET QPs.

The hint is provided through new QP creation flag called NETIF_QP.

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