xhci: Make sure xhci handles USB_SPEED_SUPER_PLUS devices.

In most cases the devices with the speed set to USB_SPEED_SUPER_PLUS
are handled like regular SuperSpeed devices.

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>