f2fs: fix to avoid f2fsbugon() in decvalidnode_count()
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 v5.10.121 by commit 2766ddaf45b69252bb8fe526b5b6e56904a9ae7a. For more details please see the references link.