IB/mlx4: Add contig support for control objects

Taking advantage of the optimization which was introduced in previous
commit ("IB/mlx4: Use optimal numbers of MTT entries") to optimize the
MTT usage for QP and CQ.

Signed-off-by: Guy Levi <guyle@mellanox.com>
Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>