r600-NI shared the same blit suspend code.  Clean it up
and make it a shared function.
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Reviewed-by: NIlija Hadzic <ihadzic@research.bell-labs.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>