usb: add device descriptor for usb 3.1 root hub

BugLink: http://bugs.launchpad.net/bugs/1519623



Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 9508e3b7)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>