Add EEPROM_BOOT_SILENT option

Marlin/Configuration.h

@@ -1446,6 +1446,7 @@
 //#define EEPROM_SETTINGS     // Persistent storage with M500 and M501
 //#define DISABLE_M503        // Saves ~2700 bytes of PROGMEM. Disable for release!
 #define EEPROM_CHITCHAT       // Give feedback on EEPROM commands. Disable to save PROGMEM.
+#define EEPROM_BOOT_SILENT    // Keep M503 quiet and only give errors during first load
 #if ENABLED(EEPROM_SETTINGS)
   //#define EEPROM_AUTO_INIT  // Init EEPROM automatically on any errors.
 #endif

Marlin/src/module/configuration_store.cpp

@@ -2185,8 +2185,10 @@ void MarlinSettings::postprocess() {
     }
 
     #if ENABLED(EEPROM_CHITCHAT) && DISABLED(DISABLE_M503)
-      if (!validating) report();
+      // Report the EEPROM settings
+      if (!validating && (DISABLED(EEPROM_BOOT_SILENT) || IsRunning())) report();
     #endif
+
     EEPROM_FINISH();
 
     return !eeprom_error;