usb: gadget: dummy_hcd: fix build when BUG is not set

Use WARN_ON() instead of __WARN, which also means we won't use any
internal macros.
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/dummy_hcd.c

@@ -598,7 +598,7 @@ static void dummy_free_request(struct usb_ep *_ep, struct usb_request *_req)
 	struct dummy_request	*req;
 
 	if (!_ep || !_req) {
-		__WARN();
+		WARN_ON(1);
 		return;
 	}