usb.h: fix kernel-doc warning

Fix kernel-doc warning in usb.h:
Warning(linux-2.6.24-rc3-git7//include/linux/usb.h:166): No description found for parameter 'sysfs_files_created'

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>