reduce CFG_TUD_DFU_XFER_BUFSIZE for max compatible

examples/device/dfu/src/tusb_config.h

@@ -80,7 +80,7 @@
 #define CFG_TUD_DFU    1
 
 // DFU buffer size, it has to be set to the buffer size used in TUD_DFU_DESCRIPTOR
-#define CFG_TUD_DFU_XFER_BUFSIZE    512
+#define CFG_TUD_DFU_XFER_BUFSIZE    ( OPT_MODE_HIGH_SPEED ? 512 : 64 )
 
 #ifdef __cplusplus
  }