net/mlx5: Add layout to support default timeouts register

Add needed structures and defines for DTOR (default timeouts register).
This will be used to get timeouts values from FW instead of hard coded
values in the driver code thus enabling support for slower devices which
need longer timeouts.

Signed-off-by: Amir Tzin <amirtz@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>