Apply #pragma once, misc cleanup (#12322)

* Apply #pragma once in headers
* Adjust some thermistors formatting
* Misc cleanup and formatting

Marlin/src/core/boards.h

@@ -19,9 +19,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-
-#ifndef BOARDS_H
-#define BOARDS_H
+#pragma once
 
 #define BOARD_UNKNOWN -1
 
@@ -247,5 +245,3 @@
 #define BOARD_ESP32            1900
 
 #define MB(board) (defined(BOARD_##board) && MOTHERBOARD==BOARD_##board)
-
-#endif // __BOARDS_H

Marlin/src/core/enum.h

@@ -19,9 +19,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-
-#ifndef __ENUM_H__
-#define __ENUM_H__
+#pragma once
 
 /**
  * Axis indices as enumerated constants
@@ -68,5 +66,3 @@ typedef enum {
   TEMPUNIT_K,
   TEMPUNIT_F
 } TempUnit;
-
-#endif // __ENUM_H__

Marlin/src/core/serial.h

@@ -19,9 +19,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-
-#ifndef __SERIAL_H__
-#define __SERIAL_H__
+#pragma once
 
 #include "../inc/MarlinConfigPre.h"
 #include HAL_PATH(../HAL, HAL.h)
@@ -246,5 +244,3 @@ void serial_error_start();
   void print_xyz(PGM_P prefix, PGM_P suffix, const float xyz[]);
   #define DEBUG_POS(SUFFIX,VAR) do { print_xyz(PSTR("  " STRINGIFY(VAR) "="), PSTR(" : " SUFFIX "\n"), VAR); } while(0)
 #endif
-
-#endif // __SERIAL_H__

Marlin/src/core/utility.h

@@ -19,9 +19,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-
-#ifndef __UTILITY_H__
-#define __UTILITY_H__
+#pragma once
 
 #include "../inc/MarlinConfigPre.h"
 
@@ -102,5 +100,3 @@ void safe_delay(millis_t ms);
 #if ENABLED(DEBUG_LEVELING_FEATURE)
   void log_machine_info();
 #endif
-
-#endif // __UTILITY_H__