[media] videobuf2: correct the #ifndef text mistake in videobuf2-dma-contig.h

It should be a mistake due to copy & paste in header file
  Correct it in videobuf2-dma-config.h for avoiding duplicate include it

Change-Id: I1f71fcec2889c033c7db380c58d9a1369c5afb35
Signed-off-by: Albert Wang <twang13@marvell.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

include/media/videobuf2-dma-contig.h

 /*
- * videobuf2-dma-coherent.h - DMA coherent memory allocator for videobuf2
+ * videobuf2-dma-contig.h - DMA contig memory allocator for videobuf2
  *
  * Copyright (C) 2010 Samsung Electronics
  *
@@ -10,8 +10,8 @@
  * the Free Software Foundation.
  */
 
-#ifndef _MEDIA_VIDEOBUF2_DMA_COHERENT_H
-#define _MEDIA_VIDEOBUF2_DMA_COHERENT_H
+#ifndef _MEDIA_VIDEOBUF2_DMA_CONTIG_H
+#define _MEDIA_VIDEOBUF2_DMA_CONTIG_H
 
 #include <media/videobuf2-core.h>
 #include <linux/dma-mapping.h>