GSD-2021-1001576 drm/amdgpu: fix gart.bo pin_count leak

drm/amdgpu: fix gart.bo pincount 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 v5.4.154 by commit 83d857d6b0967b6709cd38750c3ce2ed8ced1a9...