mtd: introduce mtd_read_oob 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/nftlcore.c b/drivers/mtd/nftlcore.c
index 1a9d9c1..7497f5e 100644
--- a/drivers/mtd/nftlcore.c
+++ b/drivers/mtd/nftlcore.c
@@ -153,7 +153,7 @@
 	ops.oobbuf = buf;
 	ops.datbuf = NULL;
 
-	res = mtd->read_oob(mtd, offs & ~mask, &ops);
+	res = mtd_read_oob(mtd, offs & ~mask, &ops);
 	*retlen = ops.oobretlen;
 	return res;
 }