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 v5.15.46 by commit bce859358d3d5940aa858e40ceee70ee6e76130e. For more details please see the references link.