usb: host: ehci: always enable interrupt for qtd completion at test mode

At former code, the SETUP stage does not enable interrupt
for qtd completion, it relies on IAA watchdog to complete
interrupt, then the transcation would be considered timeout
if the flag need_io_watchdog is cleared by platform code.

In this commit, we always add enable interrupt for qtd completion,
then the qtd completion can be notified by hardware interrupt.

Signed-off-by: Peter Chen <peter.chen@nxp.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>