USB: Make sure to fetch the BOS desc for roothubs.

The BOS descriptor is normally fetched and stored in the usb_device->bos
during enumeration.  USB 3.0 roothubs don't undergo enumeration, but we
need them to have a BOS descriptor, since each xHCI host has a different
U1 and U2 exit latency.  Make sure to fetch the BOS descriptor for USB
3.0 roothubs.  It will be freed when the roothub usb_device is released.
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Andiry Xu <andiry.xu@amd.com>

drivers/usb/core/hcd.c

@@ -997,6 +997,15 @@ static int register_root_hub(struct usb_hcd *hcd)
 				dev_name(&usb_dev->dev), retval);
 		return (retval < 0) ? retval : -EMSGSIZE;
 	}
+	if (usb_dev->speed == USB_SPEED_SUPER) {
+		retval = usb_get_bos_descriptor(usb_dev);
+		if (retval < 0) {
+			mutex_unlock(&usb_bus_list_lock);
+			dev_dbg(parent_dev, "can't read %s bos descriptor %d\n",
+					dev_name(&usb_dev->dev), retval);
+			return retval;
+		}
+	}
 
 	retval = usb_new_device (usb_dev);
 	if (retval) {