Apply #pragma once, misc cleanup (#12322)

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

Marlin/src/libs/buzzer.h

@@ -19,9 +19,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-
-#ifndef __BUZZER_H__
-#define __BUZZER_H__
+#pragma once
 
 #include "../inc/MarlinConfig.h"
 
@@ -123,5 +121,3 @@ class Buzzer {
   #define BUZZ(d,f) NOOP
 
 #endif
-
-#endif