null_blk: Fix zoned command return code

The return code from null_handle_zoned() sets the cmd->error value.
Returning OK status when an error occured overwrites the intended
cmd->error. Return the appropriate error code instead of setting the
error in the cmd.

Fixes: fceb5d1b19 ("null_blk: create a helper for zoned devices")
Cc: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/null_blk_zoned.c

@@ -142,8 +142,7 @@ static blk_status_t null_zone_reset(struct nullb_cmd *cmd, sector_t sector)
 		zone->wp = zone->start;
 		break;
 	default:
-		cmd->error = BLK_STS_NOTSUPP;
-		break;
+		return BLK_STS_NOTSUPP;
 	}
 	return BLK_STS_OK;
 }