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/nftlmount.c b/drivers/mtd/nftlmount.c
index b068dc8..156af9f 100644
--- a/drivers/mtd/nftlmount.c
+++ b/drivers/mtd/nftlmount.c
@@ -242,7 +242,8 @@
 			if (buf[i & (SECTORSIZE - 1)] != 0xff)
 				nftl->ReplUnitTable[i] = BLOCK_RESERVED;
 #endif
-			if (nftl->mbd.mtd->block_isbad(nftl->mbd.mtd, i * nftl->EraseSize))
+			if (mtd_block_isbad(nftl->mbd.mtd,
+					    i * nftl->EraseSize))
 				nftl->ReplUnitTable[i] = BLOCK_RESERVED;
 		}