drm/i915: Ironlake page-flipping is per-plane not per-pipe

Fix a minor confusion between intel_page_flip_finish(pipe) and
intel_page_flip_finish_plane(plane) -- should have no effect as
currently we map pipe 0 to plane 0 (and pipe 1 to plane 1).

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
1 file changed