CVE-2021-47431 drm/amdgpu: fix gart.bo pin_count leak

In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu: fix gart.bo pincount leak gmcv9,100gartdisable isn't called matched with correspoding gartenbale function in SRIOV case. This will lead to gart.bo pincount leak on driver unload...