GSD-2022-1004487 ext4: make variable "count" signed

ext4: make variable "count" signed 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 v5.15.49 by commit 4fadac8c73764436a3434acf324b4d213d5bd281, ...