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/rfd_ftl.c b/drivers/mtd/rfd_ftl.c
index 5426d42..233b946 100644
--- a/drivers/mtd/rfd_ftl.c
+++ b/drivers/mtd/rfd_ftl.c
@@ -448,8 +448,7 @@
 	int rc;
 
 	/* we have a race if sync doesn't exist */
-	if (part->mbd.mtd->sync)
-		mtd_sync(part->mbd.mtd);
+	mtd_sync(part->mbd.mtd);
 
 	score = 0x7fffffff; /* MAX_INT */
 	best_block = -1;