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>

drivers/gpu/drm/i915/i915_irq.c

@@ -351,12 +351,12 @@ irqreturn_t ironlake_irq_handler(struct drm_device *dev)
 
 	if (de_iir & DE_PLANEA_FLIP_DONE) {
 		intel_prepare_page_flip(dev, 0);
-		intel_finish_page_flip(dev, 0);
+		intel_finish_page_flip_plane(dev, 0);
 	}
 
 	if (de_iir & DE_PLANEB_FLIP_DONE) {
 		intel_prepare_page_flip(dev, 1);
-		intel_finish_page_flip(dev, 1);
+		intel_finish_page_flip_plane(dev, 1);
 	}
 
 	if (de_iir & DE_PIPEA_VBLANK)