usb: dwc3: remove special status request handling in ep0

The GetStatus (STD)-request is handled the driver and uses a tiny hack
to send the two bytes long answer. This patch removes the custom hack
uses the normal usb_ep_queue() for that.

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