DFU: Add missing 'return' after handling generic USB control request

firmware/atmel_softpack_libraries/usb/device/dfu/dfu_driver.c

@@ -248,6 +248,7 @@ void USBDFU_DFU_RequestHandler(const USBGenericRequest *request)
 	    USBGenericRequest_GetRecipient(request) != USBGenericRequest_INTERFACE) {
 		TRACE_DEBUG("std_ho_usbd ");
 		USBDDriver_RequestHandler(&usbdDriver, request);
+		return;
 	}
 
 	switch (g_dfu->state) {