drm/doc: integrate drm_crtc.c kerneldoc

And do a quick pass to adjust them to the last few (years?) of changes
...

This time actually compile-tested ;-)

Reviewed-by: Rob Clark <rob@ti.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index 4ee2304..caab791 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -1609,6 +1609,10 @@
         make its properties available to applications.
       </para>
     </sect2>
+    <sect2>
+      <title>KMS API Functions</title>
+!Edrivers/gpu/drm/drm_crtc.c
+    </sect2>
   </sect1>
 
   <!-- Internals: kms helper functions -->