CVE-2022-50578 class: fix possible memory leak in __class_register()

In the Linux kernel, the following vulnerability has been resolved: class: fix possible memory leak in classregister If classaddgroups returns error, the 'cp-subsys' need be unregister, and the 'cp' need be freed. We can not call ksetunregister here, because the 'cls' will be freed in callback...