IB/mlx5: Set QP offsets and parameters for user QPs and not just for kernel QPs

For user QPs, the creation process does not currently initialize the fields:

 * qp->rq.offset
 * qp->sq.offset
 * qp->sq.wqe_shift

Signed-off-by: Haggai Eran <haggaie@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>