esp32: Fix ARDUINO_NANO_ESP32 build configuration.

Regression introduced by 5e692d04 now at MICROPY_HW_USB_CDC is set.

The ARDUINO_NANO_ESP32 specifically builds shared/tinyusb/mp_usb_cdc.c
for the 1200bps reset behaviour. However MicroPython esp32 doesn't yet
use the rest of the shared/tinyusb functionality.
Signed-off-by: Angus Gratton <angus@redyak.com.au>

ports/esp32/boards/ARDUINO_NANO_ESP32/mpconfigboard.h

@@ -19,6 +19,7 @@
 #define MICROPY_HW_SPI2_SCK                 (18)
 
 #define MICROPY_HW_ENABLE_USBDEV            (1)
+#define MICROPY_EXCLUDE_SHARED_TINYUSB_USBD_CDC (1)
 #define MICROPY_HW_USB_EXTERNAL_TINYUSB     (1)
 #define MICROPY_HW_USB_CDC_1200BPS_TOUCH    (1)
 #define MICROPY_SCHEDULER_STATIC_NODES      (1)