test: Convert to pragma once

Remove the verbose #ifndef/#define/#endif pattern for maintaining
header idempotency, and replace it with a simple #pragma once.

This simplifies the headers, and prevents redundant changes when
header files get moved.

Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>

test/serialization/serialization_test.h

@@ -4,8 +4,8 @@
  *
  * serialization_test.h - Base class for serialization tests
  */
-#ifndef __LIBCAMERA_SERIALIZATION_TEST_H__
-#define __LIBCAMERA_SERIALIZATION_TEST_H__
+
+#pragma once
 
 #include <libcamera/camera.h>
 #include <libcamera/camera_manager.h>
@@ -27,5 +27,3 @@ public:
 	static bool equals(const libcamera::ControlList &lhs,
 			   const libcamera::ControlList &rhs);
 };
-
-#endif /* __LIBCAMERA_SERIALIZATION_TEST_H__ */