xhci: Modify check for TT info.

Commit d199c96d by Alan Stern ensured that low speed and full speed
devices below a high speed hub without a transaction translator (TT) would
never get enumerated.  Simplify the check for a TT in the xHCI virtual
device allocation to only check if the usb_device references a parent's
TT.

Make sure not to set the TT information on LS/FS devices directly
connected to the roothub.  The xHCI host doesn't really have a TT, and the
host will throw an error when those virtual device TT fields are set for a
device connected to the roothub.  We need this check because the xHCI
driver will shortly register two roothubs: a USB 2.0 roothub and a USB 3.0
roothub.
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

drivers/usb/host/xhci-mem.c

@@ -870,9 +870,8 @@ int xhci_setup_addressable_virt_dev(struct xhci_hcd *xhci, struct usb_device *ud
 	dev->port = top_dev->portnum;
 	xhci_dbg(xhci, "Set root hub portnum to %d\n", top_dev->portnum);
 
-	/* Is this a LS/FS device under a HS hub? */
-	if ((udev->speed == USB_SPEED_LOW || udev->speed == USB_SPEED_FULL) &&
-			udev->tt) {
+	/* Is this a LS/FS device under an external HS hub? */
+	if (udev->tt && udev->tt->hub->parent) {
 		slot_ctx->tt_info = udev->tt->hub->slot_id;
 		slot_ctx->tt_info |= udev->ttport << 8;
 		if (udev->tt->multi)