drm/doc: Remove outdated FIXME for the page_flip callback

Since the drm_event cleanup work (as prep for fence support) drivers
don't need to bother themselves any more with this, the drm event core
takes care of that.

Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1471034937-651-8-git-send-email-daniel.vetter@ffwll.ch

include/drm/drm_crtc.h

@@ -547,16 +547,6 @@ struct drm_crtc_funcs {
 	 * counter and timestamp tracking though, e.g. if they have accurate
 	 * timestamp registers in hardware.
 	 *
-	 * FIXME:
-	 *
-	 * Up to that point drivers need to manage events themselves and can use
-	 * even->base.list freely for that. Specifically they need to ensure
-	 * that they don't send out page flip (or vblank) events for which the
-	 * corresponding drm file has been closed already. The drm core
-	 * unfortunately does not (yet) take care of that. Therefore drivers
-	 * currently must clean up and release pending events in their
-	 * ->preclose driver function.
-	 *
 	 * This callback is optional.
 	 *
 	 * NOTE: