drm: Include drm_crtc_helper.h in DocBook

There is already a section that describes the helpers implemented by
this module. Add the kerneldoc-generated structure descriptions to this
section.

While at it, add missing kerneldoc for the structures to avoid warnings
when generating the documentation.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index d45b267..7af413f 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -2362,6 +2362,7 @@
     </sect2>
     <sect2>
       <title>Modeset Helper Functions Reference</title>
+!Iinclude/drm/drm_crtc_helper.h
 !Edrivers/gpu/drm/drm_crtc_helper.c
 !Pdrivers/gpu/drm/drm_crtc_helper.c overview
     </sect2>