[media] v4l2-mc.h: prevent it for being included twice

Don't let it be included twice, to avoid compiler issues.
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

include/media/v4l2-mc.h

@@ -14,6 +14,9 @@
  * GNU General Public License for more details.
  */
 
+#ifndef _V4L2_MC_H
+#define _V4L2_MC_H
+
 #include <media/media-device.h>
 
 /**
@@ -136,3 +139,5 @@ struct media_device *v4l2_mc_pci_media_device_init(struct pci_dev *pci_dev,
 }
 
 #endif
+
+#endif