usb: usbtest: Add timetout to simple_io()

Without a timetout some tests e.g. test_halt() can remain stuck forever.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>