drm/doc: Fix more kerneldoc/sphinx warnings

These are the leftovers I could only track down using keep_warnings =
True. For some of them we might want to update our style guide on how
to reference structures and constants, not sure ...

Cc: Markus Heiser <markus.heiser@darmarit.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1471034937-651-1-git-send-email-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_fb_helper.c

@@ -2193,7 +2193,7 @@ EXPORT_SYMBOL(drm_fb_helper_initial_config);
  * @fb_helper: the drm_fb_helper
  *
  * Scan the connectors attached to the fb_helper and try to put together a
- * setup after *notification of a change in output configuration.
+ * setup after notification of a change in output configuration.
  *
  * Called at runtime, takes the mode config locks to be able to check/change the
  * modeset configuration. Must be run from process context (which usually means