drm/i915/sprite: Always enable the scaler on IronLake

As I do not see the output update without the scaler enabled on my
i3-330m, always enable it.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>