xhci: set roothub speed to USB_SPEED_SUPER_PLUS for USB3.1 capable controllers

BugLink: http://bugs.launchpad.net/bugs/1519623Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 2c0e06f8)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/usb/host/xhci.c

@@ -4883,6 +4883,7 @@ int xhci_gen_setup(struct usb_hcd *hcd, xhci_get_quirks_t get_quirks)
 		if (xhci->sbrn == 0x31) {
 			xhci_info(xhci, "Host supports USB 3.1 Enhanced SuperSpeed\n");
 			hcd->speed = HCD_USB31;
+			hcd->self.root_hub->speed = USB_SPEED_SUPER_PLUS;
 		}
 		/* xHCI private pointer was set in xhci_pci_probe for the second
 		 * registered roothub.