mtd: return success on blktrans_ioctl

There was a break missing so we returned -ENOTTY on success instead of
zero.  This was introduced by 048d8719: "mtd: blktrans: Hotplug fixes"
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/mtd_blkdevs.c

@@ -245,6 +245,7 @@ static int blktrans_ioctl(struct block_device *bdev, fmode_t mode,
 	switch (cmd) {
 	case BLKFLSBUF:
 		ret = dev->tr->flush ? dev->tr->flush(dev) : 0;
+		break;
 	default:
 		ret = -ENOTTY;
 	}