drm/doc: Remove the "command submissin and fencing" section

This should be done in the driver chapter instead.
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Documentation/DocBook/drm.tmpl

@@ -2585,16 +2585,6 @@ int num_ioctls;</synopsis>
     </sect2>
   </sect1>
 
-  <sect1>
-    <title>Command submission &amp; fencing</title>
-    <para>
-      This should cover a few device-specific command submission
-      implementations.
-    </para>
-  </sect1>
-
-  <!-- Internals: suspend/resume -->
-
   <sect1>
     <title>Suspend/Resume</title>
     <para>