esp32: Enable machine.USBDevice to configure USB at runtime.

This adds support for `machine.USBDevice` to S2 and S3 boards.

Signed-off-by: Sebastian Romero <s.romero@arduino.cc>
diff --git a/ports/esp32/mpconfigport.h b/ports/esp32/mpconfigport.h
index bf1f5a1..b5b7d63 100644
--- a/ports/esp32/mpconfigport.h
+++ b/ports/esp32/mpconfigport.h
@@ -215,6 +215,10 @@
 #else
 #define MICROPY_HW_USB_VID  (CONFIG_TINYUSB_DESC_CUSTOM_VID)
 #endif
+
+#ifndef MICROPY_HW_ENABLE_USB_RUNTIME_DEVICE
+#define MICROPY_HW_ENABLE_USB_RUNTIME_DEVICE    (1) // Support machine.USBDevice
+#endif
 #endif
 
 #ifndef MICROPY_HW_USB_PID