mtd: introduce mtd_write_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/inftlcore.c b/drivers/mtd/inftlcore.c
index 07646e1..28646c9 100644
--- a/drivers/mtd/inftlcore.c
+++ b/drivers/mtd/inftlcore.c
@@ -178,7 +178,7 @@
 	ops.oobbuf = buf;
 	ops.datbuf = NULL;
 
-	res = mtd->write_oob(mtd, offs & ~(mtd->writesize - 1), &ops);
+	res = mtd_write_oob(mtd, offs & ~(mtd->writesize - 1), &ops);
 	*retlen = ops.oobretlen;
 	return res;
 }
@@ -199,7 +199,7 @@
 	ops.datbuf = buf;
 	ops.len = len;
 
-	res = mtd->write_oob(mtd, offs & ~(mtd->writesize - 1), &ops);
+	res = mtd_write_oob(mtd, offs & ~(mtd->writesize - 1), &ops);
 	*retlen = ops.retlen;
 	return res;
 }