mtd: introduce mtd_writev 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/mtdconcat.c b/drivers/mtd/mtdconcat.c
index 3d9c1ff..6fdae19 100644
--- a/drivers/mtd/mtdconcat.c
+++ b/drivers/mtd/mtdconcat.c
@@ -227,8 +227,9 @@
 		if (!(subdev->flags & MTD_WRITEABLE))
 			err = -EROFS;
 		else
-			err = subdev->writev(subdev, &vecs_copy[entry_low],
-				entry_high - entry_low + 1, to, &retsize);
+			err = mtd_writev(subdev, &vecs_copy[entry_low],
+					 entry_high - entry_low + 1, to,
+					 &retsize);
 
 		vecs_copy[entry_high].iov_len = old_iov_len - size;
 		vecs_copy[entry_high].iov_base += size;