drm/atomic: doc: remove old comment about nonblocking commits

We now support nonblocking commits on drm_atomic_helper_commit()
so the comment is not valid anymore.

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1480946626-30917-1-git-send-email-gustavo@padovan.org

drivers/gpu/drm/drm_atomic_helper.c

@@ -1234,9 +1234,6 @@ static void commit_work(struct work_struct *work)
  * function implements nonblocking commits, using
  * drm_atomic_helper_setup_commit() and related functions.
  *
- * Note that right now this function does not support nonblocking commits, hence
- * driver writers must implement their own version for now.
- *
  * Committing the actual hardware state is done through the
  * ->atomic_commit_tail() callback of the &drm_mode_config_helper_funcs vtable,
  * or it's default implementation drm_atomic_helper_commit_tail().