Add firmware test

Uncomment #define FIRMWARE_TEST in configurations.h for start tools test
firmware. Use 115200 baudrate and serial monitori of arduino tools.

MarlinKimbra/Marlin_main.cpp

@@ -694,6 +694,9 @@ void setup()
   pinMode(SERVO0_PIN, OUTPUT);
   digitalWrite(SERVO0_PIN, LOW); // turn it off
 #endif // Z_PROBE_SLED
+#ifdef FIRMWARE_TEST
+  FirmwareTest();
+#endif // FIRMWARE_TEST
 }
 
 
@@ -5016,11 +5019,6 @@ case 404:  //M404 Enter the nominal filament width (3mm, 1.75mm ) N<3.0> or disp
       }
       break;
 #endif // NPR2
-#ifdef FIRMWARE_TEST
-      case 998: // M998 Firmware test
-        FirmwareTest();
-      break;
-#endif // FIRMWARE_TEST
       case 999: // M999: Restart after being stopped
         Stopped = false;
         lcd_reset_alert_level();

README.md

@@ -183,7 +183,7 @@ Set distance to probe bed at for G30 function
 * \#define BED_DIAMETER 170 // mm
 
 
-M998 Firmware test tools
+Firmware test tools
 -----------------
 Test firmware uncomment
 * \#define FIRMWARE_TEST in configuration.h
@@ -301,7 +301,6 @@ M Codes
 *  M350 - Set microstepping mode.
 *  M351 - Toggle MS1 MS2 pins directly.
 *  M928 - Start SD logging (M928 filename.g) - ended by M29
-*  M998 - Start tools firmware test
 *  M999 - Restart after being stopped by error