usb: hub: Change USB hub descriptor to match USB 3.0 hubs

usb: hub: Change USB hub descriptor to match USB 3.0 hubs

USB 3.0 hubs have a slightly different hub descriptor than USB 2.0
hubs, with a fixed (rather than variable length) size. Change the
host controller drivers that access those last two fields
(DeviceRemovable and PortPowerCtrlMask) to use the union.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Stefan Roese <sr@denx.de>