Add DFU Class per Version 1.1 Spec

src/device/usbd.c

@@ -1,4 +1,4 @@
-/* 
+/*
  * The MIT License (MIT)
  *
  * Copyright (c) 2019 Ha Thach (tinyusb.org)
@@ -182,7 +182,7 @@ static usbd_class_driver_t const _usbd_driver[] =
     .reset            = dfu_rtd_reset,
     .open             = dfu_rtd_open,
     .control_xfer_cb  = dfu_rtd_control_xfer_cb,
-    .xfer_cb          = dfu_rtd_xfer_cb,
+    .xfer_cb          = NULL,
     .sof              = NULL
   },
   #endif
@@ -1270,9 +1270,9 @@ bool usbd_edpt_stalled(uint8_t rhport, uint8_t ep_addr)
 
 /**
  * usbd_edpt_close will disable an endpoint.
- * 
+ *
  * In progress transfers on this EP may be delivered after this call.
- * 
+ *
  */
 void usbd_edpt_close(uint8_t rhport, uint8_t ep_addr)
 {