drm/amdgpu: remove owner cleanup v2

The client ID is now unique, so no need to resert the owner fields any more.

v2: remove unused variables as well

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Chunming Zhou <david1.zhou@amd.com> (v1)
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>