drm/i915: VLV does not have a sprite scaler

Just like HSW, VLV does not have a sprite scale. Set
intel_plane->can_scale accordingly.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>