net/mlx4_core: set used number of MTTs when using auto-detection

net/mlx4_core: set used number of MTTs when using auto-detection

Issue 31158.

If we set the number of MTTs automatically by the driver (default
value or auto-detection, by the memory size in the machine), need
to set the used value of the MTTs, so the user will see this value.

Signed-off-by: Dotan Barak <dotanb@dev.mellanox.co.il>
Reviewed-by: Yishai Hadas <yishaih@mellanox.com>
(Ported from Mellanox OFED 2.4)

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