remove mentionings of devfs in documentation

Now that devfs is removed, there's no longer any need to document how to
do this or that with devfs.

This patch includes some improvements by Joe Perches.

Signed-off-by: Adrian Bunk <bunk@stusta.de>

Documentation/DocBook/usb.tmpl

@@ -314,8 +314,7 @@
 	<emphasis>usbdevfs</emphasis> although it wasn't solving what
 	<emphasis>devfs</emphasis> was.
 	Every USB device will appear in usbfs, regardless of whether or
-	not it has a kernel driver; but only devices with kernel drivers
-	show up in devfs.
+	not it has a kernel driver.
 	</para>
 
 	<sect1>

Documentation/DocBook/writing_usb_driver.tmpl

@@ -224,13 +224,8 @@ static int skel_probe(struct usb_interface *interface,
      Conversely, when the device is removed from the USB bus, the disconnect
      function is called with the device pointer. The driver needs to clean any
      private data that has been allocated at this time and to shut down any
-     pending urbs that are in the USB system. The driver also unregisters
-     itself from the devfs subsystem with the call:
+     pending urbs that are in the USB system.
   </para>
-  <programlisting>
-/* remove our devfs node */
-devfs_unregister(skel->devfs);
-  </programlisting>
   <para>
      Now that the device is plugged into the system and the driver is bound to
      the device, any of the functions in the file_operations structure that