mtd: introduce mtd_block_markbad interface

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/drivers/mtd/mtdconcat.c b/drivers/mtd/mtdconcat.c
index d0db5e6..f694b51 100644
--- a/drivers/mtd/mtdconcat.c
+++ b/drivers/mtd/mtdconcat.c
@@ -693,7 +693,7 @@
 			continue;
 		}
 
-		err = subdev->block_markbad(subdev, ofs);
+		err = mtd_block_markbad(subdev, ofs);
 		if (!err)
 			mtd->ecc_stats.badblocks++;
 		break;