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/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
index 8610750..0e7dfc7 100644
--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -322,7 +322,7 @@
 	if (ofs >= mtd->size)
 		return -EINVAL;
 	ofs += part->offset;
-	return part->master->block_isbad(part->master, ofs);
+	return mtd_block_isbad(part->master, ofs);
 }
 
 static int part_block_markbad(struct mtd_info *mtd, loff_t ofs)
@@ -553,8 +553,7 @@
 		uint64_t offs = 0;
 
 		while (offs < slave->mtd.size) {
-			if (master->block_isbad(master,
-						offs + slave->offset))
+			if (mtd_block_isbad(master, offs + slave->offset))
 				slave->mtd.ecc_stats.badblocks++;
 			offs += slave->mtd.erasesize;
 		}