mlx4_core: sysfs, fix usage of log_num_mtt module parameter

mlx4_core: sysfs, fix usage of log_num_mtt module parameter

When was auto calculated based on RAM size it wrongly includes
also log_mtts_per_seg.

It's wrong in 2 ways:
First, log_mtts_per_seg should be added by the application itself,
no reason to a have total in log_num_mtt itself.
Second, in case that an extra  NIC exists it may get an invalid
value as it depends on a larger value.
Specifically, it may cause an overflow and later leads on to
kernel panic via mlx4_buddy_init.

Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
(Ported from Mellanox OFED 2.4)

Signed-off-by: Mukesh Kacker <mukesh.kacker@oracle.com>