CVE-2025-40339 drm/amdgpu: fix nullptr err of vm_handle_moved

In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu: fix nullptr err of vmhandlemoved If a amdgpubova is fpriv-prtva, the bo of this one is always NULL. So, such kind of amdgpubova should be updated separately before amdgpuvmhandlemoved...