net/mlx5: Read timeout values from DTOR

Replace hard coded timeouts with values stored by firmware in default
timeouts register (DTOR). Timeouts are read during driver load. If DTOR
is not supported by firmware then fallback to hard coded defaults
instead.

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