usb: chipidea: host: disable io watchdog

The Chipidea EHCI core seems to behave sanely and doesn't need
the IO watchdog. This kills off 10 non-deferrable wakeup events
per second when the controller is otherwise idle.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Tested-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Peter Chen <peter.chen@nxp.com>