v4l2: 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/v4l2/v4l2_camera.h

@@ -5,8 +5,7 @@
  * v4l2_camera.h - V4L2 compatibility camera
  */
 
-#ifndef __V4L2_CAMERA_H__
-#define __V4L2_CAMERA_H__
+#pragma once
 
 #include <deque>
 #include <mutex>
@@ -86,5 +85,3 @@ private:
 	std::condition_variable bufferCV_;
 	unsigned int bufferAvailableCount_;
 };
-
-#endif /* __V4L2_CAMERA_H__ */