mtd: introduce mtd_block_isbad interface

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/fs/jffs2/scan.c b/fs/jffs2/scan.c
index 72f3960..83e1665 100644
--- a/fs/jffs2/scan.c
+++ b/fs/jffs2/scan.c
@@ -455,7 +455,7 @@
 	if (jffs2_cleanmarker_oob(c)) {
 		int ret;
 
-		if (c->mtd->block_isbad(c->mtd, jeb->offset))
+		if (mtd_block_isbad(c->mtd, jeb->offset))
 			return BLK_STATE_BADBLOCK;
 
 		ret = jffs2_check_nand_cleanmarker(c, jeb);