Fix Lolin S2 USB CDC setup (#1251)

This commit fixes an issue with this board pointed out in ESP32 Arduino Github.

espressif/arduino-esp32#8977 (comment)

Author: SuGlider

boards/lolin_s2_mini.json

@@ -7,7 +7,8 @@
     "extra_flags": [
       "-DARDUINO_LOLIN_S2_MINI",
       "-DBOARD_HAS_PSRAM",
-      "-DARDUINO_USB_CDC_ON_BOOT=1"
+      "-DARDUINO_USB_CDC_ON_BOOT=1",
+      "-DARDUINO_USB_MODE=0"
     ],
     "f_cpu": "240000000L",
     "f_flash": "80000000L",