IB/mlx4: Create and use another QP1 for RoCEv2

The mlx4 driver uses a special QP to implement the GSI QP. This kind
of QP allows to build the InfiniBand headers in software.
When mlx4 hardware builds the packet, it calculates the ICRC and puts
it at the end of the payload. However, this ICRC calculation depends
on the QP configuration, which is determined when the QP is modified
(roce_mode during INIT->RTR).
When receiving a packet, the ICRC verification doesn't depend on this
configuration.
Therefore, using two GSI QPs for send (one for each RoCE version) and
one GSI QP for receive are required.

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