char: xillybus: fix a refcount leak in cleanup_dev()
This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v5.15.47 by commit bc8fceda3b89006e8a7dda8a097d36045d044c25. For more details please see the references link.