libobs/media-io: Add #pragma once to video-frame.h

libobs/media-io/video-frame.h

@@ -15,6 +15,8 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ******************************************************************************/
 
+#pragma once
+
 #include "../util/bmem.h"
 #include "video-io.h"