usb: dwc3: ep0: push ep0state into xfernotready processing

We wait for the XferNotReady before we start the transfer and by then we
know ep0 state in which we supposed to be.
This is some cleanup work for the following patch in which we require to
know the ep0 state before the transfer completes.
While here, also change the argument to dwc3_ep0_do_control_status() so
we don't require the complete event structure but only the required
piece of information.

Inspired-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>