cpu_interrupt_handler: Remove #pragma once from .cpp file

src/core/arm/cpu_interrupt_handler.cpp

@@ -2,8 +2,6 @@
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
-#pragma once
-
 #include "common/thread.h"
 #include "core/arm/cpu_interrupt_handler.h"