mtd: introduce mtd_suspend 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 272ebc0..36bb1c9 100644
--- a/drivers/mtd/mtdconcat.c
+++ b/drivers/mtd/mtdconcat.c
@@ -631,7 +631,7 @@
 
 	for (i = 0; i < concat->num_subdev; i++) {
 		struct mtd_info *subdev = concat->subdev[i];
-		if ((rc = subdev->suspend(subdev)) < 0)
+		if ((rc = mtd_suspend(subdev)) < 0)
 			return rc;
 	}
 	return rc;