Use "reset reason" defines (#18462)

Marlin/src/HAL/STM32F1/HAL.cpp

 
 /**
  * TODO: Check this and change or remove.
- * currently returns 1 that's equal to poweron reset.
  */
-uint8_t HAL_get_reset_source() { return 1; }
+uint8_t HAL_get_reset_source() { return RST_POWER_ON; }
 
 void _delay_ms(const int delay_ms) { delay(delay_ms); }
 

Marlin/src/MarlinCore.cpp

 
   // Check startup - does nothing if bootloader sets MCUSR to 0
   const byte mcu = HAL_get_reset_source();
-  if (mcu &  1) SERIAL_ECHOLNPGM(STR_POWERUP);
-  if (mcu &  2) SERIAL_ECHOLNPGM(STR_EXTERNAL_RESET);
-  if (mcu &  4) SERIAL_ECHOLNPGM(STR_BROWNOUT_RESET);
-  if (mcu &  8) SERIAL_ECHOLNPGM(STR_WATCHDOG_RESET);
-  if (mcu & 32) SERIAL_ECHOLNPGM(STR_SOFTWARE_RESET);
+  if (mcu & RST_POWER_ON) SERIAL_ECHOLNPGM(STR_POWERUP);
+  if (mcu & RST_EXTERNAL) SERIAL_ECHOLNPGM(STR_EXTERNAL_RESET);
+  if (mcu & RST_BROWN_OUT) SERIAL_ECHOLNPGM(STR_BROWNOUT_RESET);
+  if (mcu & RST_WATCHDOG) SERIAL_ECHOLNPGM(STR_WATCHDOG_RESET);
+  if (mcu & RST_SOFTWARE) SERIAL_ECHOLNPGM(STR_SOFTWARE_RESET);
   HAL_clear_reset_source();
 
   serialprintPGM(GET_TEXT(MSG_MARLIN));