drm/i915/fbc: call intel_fbc_pre_update earlier during page flips

Make sure we do the pre_update - which also deactivates FBC - before
we actually schedule the page flip, just to make sure we don't
flip to the new FB with FBC still activated for the previous FB.

Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1453210558-7875-24-git-send-email-paulo.r.zanoni@intel.com

drivers/gpu/drm/i915/intel_display.c

@@ -11617,6 +11617,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 
 	crtc->primary->fb = fb;
 	update_state_fb(crtc->primary);
+	intel_fbc_pre_update(intel_crtc);
 
 	work->pending_flip_obj = obj;
 
@@ -11701,7 +11702,6 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 			  to_intel_plane(primary)->frontbuffer_bit);
 	mutex_unlock(&dev->struct_mutex);
 
-	intel_fbc_pre_update(intel_crtc);
 	intel_frontbuffer_flip_prepare(dev,
 				       to_intel_plane(primary)->frontbuffer_bit);