Update HardwareSerial.h

Author: Jason2866

Diff for: cores/esp32/HardwareSerial.h

@@ -156,10 +156,10 @@ extern void serialEventRun(void) __attribute__((weak));
 #define ARDUINO_USB_CDC_ON_BOOT 0
 #endif
 #if ARDUINO_USB_CDC_ON_BOOT //Serial used for USB CDC
-#if !ARDUINO_USB_MODE
 #include "USB.h"
 #include "USBCDC.h"
-#endif
+extern HardwareSerial Serial0;
+#elif ARDUINO_HW_CDC_ON_BOOT
 extern HardwareSerial Serial0;
 #else
 extern HardwareSerial Serial;