configfs: fix a race in configfs_{,un}register_subsystem()
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 v5.15.26 by commit e7a66dd2687758718eddd79b542a95cf3aa488cc, it was introduced in version v2.6.16 by commit 7063fbf2261194f72ee75afca67b3b38b554b5fa. For more details please see the references link.