Support for Debug Codes - Dnnn (#19225)

Co-authored-by: Scott Lahteine <thinkyhead@users.noreply.github.com>

Marlin/src/HAL/AVR/HAL.h

@@ -120,6 +120,8 @@ void HAL_init();
 inline void HAL_clear_reset_source() { MCUSR = 0; }
 inline uint8_t HAL_get_reset_source() { return MCUSR; }
 
+inline void HAL_reboot() {}  // reboot the board or restart the bootloader
+
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wunused-function"
 extern "C" {