vfio: Register/unregister container for CPR only once for each container

vfio: Register/unregister container for CPR only once for each container

vfio_cpr_register_container and vfio_cpr_unregister_container are container
scoped function. Calling them for each device attaching/detaching would
corrupt CPR reboot notifier list, i.e., when two VFIO devices are attached
to same container and have same notifier registered twice.

Fixes: d9fa4223b30a ("vfio: register container for cpr")
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250424063355.3855174-1-zhenzhong.duan@intel.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>