USB: xhci: Set route string for all devices.

The xHCI driver needs to set the route string in the slot context of all
devices, not just SuperSpeed devices.  The route string concept was added
in the USB 3.0 specification, section 10.1.3.2.  Each hub in the topology
is expected to have no more than 15 ports in order for the route string of
a device to be unique.  SuperSpeed hubs are restricted to only having 15
ports, but FS/LS/HS hubs are not.  The xHCI specification says that if the
port number the device is under is greater than 15, that portion of the
route string shall be set to 15.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>