drm/amdgpu: only apply gds clearing workaround when ras is supported

gds clearing workaround should only be applied on asics that support gfx ras

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>