FROMLIST: usb: dwc2: resume root hub to handle disconnect of device

FROMLIST: usb: dwc2: resume root hub to handle disconnect of device

When handle disconnect of the hcd during bus_suspend, hcd
needs to resume its root hub, otherwise the root hub will
not disconnect the existing devices under its port.

This issue always happens when connecting with usb devices
which support auto-suspend function (e.g. usb hub).

(am from https://patchwork.kernel.org/patch/9751469/)
Change-Id: I663fdea73f36e89130d9a250612363968cbff941
Signed-off-by: William Wu <william.wu@rock-chips.com>