drm/i915: Do not wait for flips in intel_crtc_disable_noatomic.

intel_crtc_disable_noatomic is called from hw readout during init, resume and possibly reset.
During init it's too early to have a page flip queued, before suspending all page flips
should be finished and during hw reset all page flips should be removed.

It's a bug when there are pending flips here, complain with WARN_ON instead of handling it.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/562507A3.3080901@linux.intel.comReviewed-by: Ander Conselvan de Oliveira <conselvan2@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -6255,7 +6255,8 @@ static void intel_crtc_disable_noatomic(struct drm_crtc *crtc)
 		return;
 
 	if (to_intel_plane_state(crtc->primary->state)->visible) {
-		intel_crtc_wait_for_pending_flips(crtc);
+		WARN_ON(intel_crtc->unpin_work);
+
 		intel_pre_disable_primary(crtc);
 	}