IB/cm: Add and use a helper function to add cm_id's to the port list

Add and use helper function add_cm_id_to_port_list() to attach
cm_id to port list.

Reviewed-by: Daniel Jurgens <danielj@mellanox.com>
Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>