Apply #pragma once, misc cleanup (#12322)

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

Marlin/src/HAL/HAL_DUE/watchdog_Due.h

@@ -19,9 +19,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-
-#ifndef WATCHDOG_DUE_H
-#define WATCHDOG_DUE_H
+#pragma once
 
 // Arduino Due core now has watchdog support
 
@@ -33,5 +31,3 @@ void watchdog_init();
 // Reset watchdog. MUST be called at least every 4 seconds after the
 // first watchdog_init or AVR will go into emergency procedures.
 inline void watchdog_reset() { watchdogReset(); }
-
-#endif // WATCHDOG_DUE_H