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>

include/linux/usb.h

@@ -107,6 +107,7 @@ enum usb_interface_condition {
  * @condition: binding state of the interface: not bound, binding
  *	(in probe()), bound to a driver, or unbinding (in disconnect())
  * @is_active: flag set when the interface is bound and not suspended.
+ * @sysfs_files_created: sysfs attributes exist
  * @needs_remote_wakeup: flag set when the driver requires remote-wakeup
  *	capability during autosuspend.
  * @dev: driver model's view of this device