Documentation: convert USB to new format

This is a conversion of the USB documentation to the Sphinx format.
No content was altered or reformatted.

Signed-off-by: Oliver <oneukum@suse.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/DocBook/Makefile

@@ -9,7 +9,7 @@
 DOCBOOKS := z8530book.xml  \
 	    kernel-hacking.xml kernel-locking.xml deviceiobook.xml \
 	    writing_usb_driver.xml networking.xml \
-	    kernel-api.xml filesystems.xml lsm.xml usb.xml kgdb.xml \
+	    kernel-api.xml filesystems.xml lsm.xml kgdb.xml \
 	    gadget.xml libata.xml mtdnand.xml librs.xml rapidio.xml \
 	    genericirq.xml s390-drivers.xml uio-howto.xml scsi.xml \
 	    debugobjects.xml sh.xml regulator.xml \