vga_switcheroo: Prettify documentation

Fix indentation of vga_switcheroo sections in gpu.tmpl.

Change section type of API documentation from "chapter" to "sect1"
so that the individual functions no longer clutter up the ToC.
Group together under a new "API" chapter.

Fix wording "heretoforth" -> "henceforth".
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Documentation/DocBook/gpu.tmpl

@@ -3635,27 +3635,27 @@ int num_ioctls;</synopsis>
     </sect1>
   </chapter>
 
-  <chapter id="pubfunctions">
+  <chapter id="api">
+    <title>API</title>
+    <sect1>
       <title>Public functions</title>
 !Edrivers/gpu/vga/vga_switcheroo.c
-  </chapter>
-
-  <chapter id="pubstructures">
+    </sect1>
+    <sect1>
       <title>Public structures</title>
 !Finclude/linux/vga_switcheroo.h vga_switcheroo_handler
 !Finclude/linux/vga_switcheroo.h vga_switcheroo_client_ops
-  </chapter>
-
-  <chapter id="pubconstants">
+    </sect1>
+    <sect1>
       <title>Public constants</title>
 !Finclude/linux/vga_switcheroo.h vga_switcheroo_client_id
 !Finclude/linux/vga_switcheroo.h vga_switcheroo_state
-  </chapter>
-
-  <chapter id="privstructures">
+    </sect1>
+    <sect1>
       <title>Private structures</title>
 !Fdrivers/gpu/vga/vga_switcheroo.c vgasr_priv
 !Fdrivers/gpu/vga/vga_switcheroo.c vga_switcheroo_client
+    </sect1>
   </chapter>
 
 !Cdrivers/gpu/vga/vga_switcheroo.c

drivers/gpu/vga/vga_switcheroo.c

@@ -63,7 +63,7 @@
  * for the inactive GPU.) Also, muxes are often used to cut power to the
  * discrete GPU while it is not used.
  *
- * DRM drivers register GPUs with vga_switcheroo, these are heretoforth called
+ * DRM drivers register GPUs with vga_switcheroo, these are henceforth called
  * clients. The mux is called the handler. Muxless machines also register a
  * handler to control the power state of the discrete GPU, its ->switchto
  * callback is a no-op for obvious reasons. The discrete GPU is often equipped