IB/mlx5: Add np_min_time_between_cnps and rp_max_rate debug params

IB/mlx5: Add np_min_time_between_cnps and rp_max_rate debug params

Add two debugfs parameters described below.

np_min_time_between_cnps - Minimum time between sending CNPs from the
                           port.
                           Unit = microseconds.
                           Default = 0 (no min wait time; generated
                           based on incoming ECN marked packets).

rp_max_rate - Maximum rate at which reaction point node can transmit.
              Once this limit is reached, RP is no longer rate limited.
              Unit = Mbits/sec
              Default = 0 (full speed)

Link: https://lore.kernel.org/r/20200227125246.99472-1-leon@kernel.org
Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>