drm/doc: Update copyright

I've done quite a bit of cleanups, clarifications and mostly
integrating kerneldoc. So I guess I should add myself.

Also split up the copyright notices per holder to make it clear which
year ranges are covered.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Documentation/DocBook/drm.tmpl

@@ -29,12 +29,26 @@
 	  </address>
 	</affiliation>
       </author>
+      <author>
+	<firstname>Daniel</firstname>
+	<surname>Vetter</surname>
+	<contrib>Contributions all over the place</contrib>
+	<affiliation>
+	  <orgname>Intel Corporation</orgname>
+	  <address>
+	    <email>daniel.vetter@ffwll.ch</email>
+	  </address>
+	</affiliation>
+      </author>
     </authorgroup>
 
     <copyright>
       <year>2008-2009</year>
-      <year>2012</year>
+      <year>2013-2014</year>
       <holder>Intel Corporation</holder>
+    </copyright>
+    <copyright>
+      <year>2012</year>
       <holder>Laurent Pinchart</holder>
     </copyright>