Apply #pragma once to configuration files

Marlin/Configuration_adv.h

@@ -19,6 +19,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
+#pragma once
 
 /**
  * Configuration_adv.h
@@ -30,8 +31,6 @@
  * Basic settings can be found in Configuration.h
  *
  */
-#ifndef CONFIGURATION_ADV_H
-#define CONFIGURATION_ADV_H
 #define CONFIGURATION_ADV_H_VERSION 020000
 
 // @section temperature
@@ -1831,5 +1830,3 @@
 
 // Enable Marlin dev mode which adds some special commands
 //#define MARLIN_DEV_MODE
-
-#endif // CONFIGURATION_ADV_H