mtd: do not use mtd->sync directly

This patch teaches 'mtd_sync()' to do nothing when the MTD driver does
not have the '->sync()' method, which allows us to remove all direct
'mtd->sync' accesses.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/drivers/mtd/ftl.c b/drivers/mtd/ftl.c
index c9c9029..19d6372 100644
--- a/drivers/mtd/ftl.c
+++ b/drivers/mtd/ftl.c
@@ -650,8 +650,7 @@
 	    if (queued) {
 		pr_debug("ftl_cs: waiting for transfer "
 		      "unit to be prepared...\n");
-		if (part->mbd.mtd->sync)
-			mtd_sync(part->mbd.mtd);
+		mtd_sync(part->mbd.mtd);
 	    } else {
 		static int ne = 0;
 		if (++ne < 5)