net/mlx5: Update log_max_qp value to be 17 at most

Currently, log_max_qp value is dependent on what FW reports as its max capability.
In reality, due to a bug, some FWs report a value greater than 17, even though they
don't support log_max_qp > 17.

This FW issue led the driver to exhaust memory on startup.
Thus, log_max_qp value is set to be no more than 17 regardless
of what FW reports, as it was before the cited commit.

Fixes: f79a609e

 ("net/mlx5: Update log_max_qp value to FW max capability")
Signed-off-by: Maher Sanalla <msanalla@nvidia.com>
Reviewed-by: Avihai Horon <avihaih@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>