mtd: introduce mtd_sync interface

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/mtdpart.c

@@ -301,7 +301,7 @@ static int part_is_locked(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 static void part_sync(struct mtd_info *mtd)
 {
 	struct mtd_part *part = PART(mtd);
-	part->master->sync(part->master);
+	mtd_sync(part->master);
 }
 
 static int part_suspend(struct mtd_info *mtd)