drm/amdgpu: fix gart.bo pin_count leak
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 v5.14.13 by commit 18d1c5ea3798ba42cfa0f8b2264d873463facb03. For more details please see the references link.