usb: gadget: udc: amd5536: do not rely on 'driver' argument

future patches will remove the extra 'driver'
argument to ->udc_stop(), in order to do that,
we must make sure that our UDC does not rely
on it first.

Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/udc/amd5536udc.c

@@ -1971,7 +1971,7 @@ static int amd5536_udc_stop(struct usb_gadget *g,
 
 	spin_lock_irqsave(&dev->lock, flags);
 	udc_mask_unused_interrupts(dev);
-	shutdown(dev, driver);
+	shutdown(dev, NULL);
 	spin_unlock_irqrestore(&dev->lock, flags);
 
 	dev->driver = NULL;