Clear user control request handlers on set_configuration request.

lib/usb/usb_standard.c

@@ -150,8 +150,15 @@ static int usb_standard_set_configuration(struct usb_setup_data *req,
 	/* Reset all endpoints. */
 	_usbd_hw_endpoints_reset();
 
-	if (_usbd_device.user_callback_set_config)
+	if (_usbd_device.user_callback_set_config) {
+		/* Flush control callbacks.  These will be reregistered
+		 * by the user handler. */
+		int i;
+		for(i = 0; i < MAX_USER_CONTROL_CALLBACK; i++)
+			_usbd_device.user_control_callback[i].cb = NULL;
+
 		_usbd_device.user_callback_set_config(req->wValue);
+	}
 
 	return 1;
 }