mtd: blkdevs: Fix mtd block write failure

All the MTD block write requests are failing with
following error messages

    mkfs.ext4  /dev/mtdblock0

    print_req_error: I/O error, dev mtdblock0, sector 0
    Buffer I/O error on dev mtdblock0, logical block 0,
    lost async page write

The control is going to default case after block write request
because of missing return.

Fixes: commit 2a842acab109 ("block: introduce new block status code type")
Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/mtd_blkdevs.c

@@ -113,6 +113,7 @@ static blk_status_t do_blktrans_request(struct mtd_blktrans_ops *tr,
 		for (; nsect > 0; nsect--, block++, buf += tr->blksize)
 			if (tr->writesect(dev, block, buf))
 				return BLK_STS_IOERR;
+		return BLK_STS_OK;
 	default:
 		return BLK_STS_IOERR;
 	}