In gem idle/busy ioctl the radeon object was derefenced after
drm_gem_object_unreference_unlocked which in case the object
have been destroyed lead to use of a possibly free pointer with
possibly wrong data.
Signed-off-by: Jerome Glisse <jglisse@redhat.com> Reviewed-by: Alex Deucher <alexander.deucher@amd.com> Reviewed-by: Christian König <christian.koenig@amd.com> Signed-off-by: Dave Airlie <airlied@redhat.com>