This is an adoption of U-Boot commit bbc6f06:

| commit bbc6f06
| Author: Bin Meng <bmeng.cn@gmail.com>
| Date:   Wed Jul 19 21:51:13 2017 +0800
|
|     usb: hub: Support 'set hub depth' request for USB 3.0 hubs
|
|     USB 3.0 hub uses a hub depth value multiplied by four as an offset
|     into the 'route string' to locate the bits it uses to determine the
|     downstream port number. We shall set the hub depth value of a USB
|     3.0 hub after it is configured.
|
|     Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
|     Reviewed-by: Simon Glass <sjg@chromium.org>

In this patch we also support recording the depth of a hub in
struct usb_device.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>