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/mtdswap.c b/drivers/mtd/mtdswap.c
index 0f0ab18..8579739 100644
--- a/drivers/mtd/mtdswap.c
+++ b/drivers/mtd/mtdswap.c
@@ -403,7 +403,7 @@
 		offset = mtdswap_eb_offset(d, eb) + d->mtd->writesize;
 	}
 
-	ret = d->mtd->write_oob(d->mtd, offset , &ops);
+	ret = mtd_write_oob(d->mtd, offset, &ops);
 
 	if (ret) {
 		dev_warn(d->dev, "Write OOB failed for block at %08llx "
@@ -946,7 +946,7 @@
 			patt = mtdswap_test_patt(test + i);
 			memset(d->page_buf, patt, mtd->writesize);
 			memset(d->oob_buf, patt, mtd->ecclayout->oobavail);
-			ret = mtd->write_oob(mtd, pos, &ops);
+			ret = mtd_write_oob(mtd, pos, &ops);
 			if (ret)
 				goto error;