android: 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>

src/android/camera_hal_manager.h

@@ -4,8 +4,8 @@
  *
  * camera_hal_manager.h - libcamera Android Camera Manager
  */
-#ifndef __ANDROID_CAMERA_MANAGER_H__
-#define __ANDROID_CAMERA_MANAGER_H__
+
+#pragma once
 
 #include <map>
 #include <mutex>
@@ -69,5 +69,3 @@ private:
 	unsigned int numInternalCameras_;
 	unsigned int nextExternalCameraId_;
 };
-
-#endif /* __ANDROID_CAMERA_MANAGER_H__ */