usb: gadget: udc: dummy: 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/dummy_hcd.c

@@ -921,9 +921,8 @@ static int dummy_udc_stop(struct usb_gadget *g,
 	struct dummy_hcd	*dum_hcd = gadget_to_dummy_hcd(g);
 	struct dummy		*dum = dum_hcd->dum;
 
-	if (driver)
 	dev_dbg(udc_dev(dum), "unregister gadget driver '%s'\n",
-				driver->driver.name);
+			dum->driver->driver.name);
 
 	dum->driver = NULL;