IB/mlx4: Use optimal numbers of MTT entries

Optimize the device performance by assigning multiple physical pages,
which are contiguous, to a single MTT. As a result, the number of MTTs
is reduced and in turn save cache misses of MTTs.

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>