🩹 Use #pragma once in pins files

Marlin/src/pins/sam/pins_CNCONTROLS_15D.h

@@ -19,6 +19,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  *
  */
+#pragma once
 
 /**
  * CNControls V15 for HMS434 with DUE pin assignments

Marlin/src/pins/sam/pins_RURAMPS4D_11.h

@@ -20,6 +20,7 @@
  *
  * Ported sys0724 & Vynt
  */
+#pragma once
 
 /**
  * Arduino Mega? or Due with RuRAMPS4DUE pin assignments

Marlin/src/pins/sam/pins_RURAMPS4D_13.h

@@ -20,6 +20,7 @@
  *
  * Ported sys0724 & Vynt
  */
+#pragma once
 
 /**
  * Arduino Mega? or Due with RuRAMPS4DUE pin assignments