IB/cm: Protect cm_dev, cm_ports and mad_agent with kref and lock

During cm_dev deregistration in cm_remove_one(), the cm_device and
cm_ports will be freed, after that they should not be accessed. The
mad_agent needs to be protected as well.

This patch adds a cm_device kref to protect cm_dev and cm_ports, and a
mad_agent_lock spinlock to protect mad_agent.

Link: https://lore.kernel.org/r/501ba7a2ff203dccd0e6755d3f93329772adce52.1622629024.git.leonro@nvidia.com


Signed-off-by: Mark Zhang <markzhang@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>