ataflop: fix error handling in atari_floppy_init()

Smatch complains that there is an off by one if the allocation fails in:

	DMABuffer = atari_stram_alloc(BUFFER_SIZE+512, "ataflop");

In that situation, "i" would be point to one element beyond the end of
the unit[] array.

There is a second bug because the error handling calls
blk_mq_free_tag_set(&unit[i].tag_set); regardless of whether
"disk->queue" is NULL or non-NULL.  So if blk_mq_init_sq_queue() fails,
then that means unit[i].tag_set->tags is NULL and it leads to an Oops.

It's easiest to call put_disk() before the goto to clean up the partial
iteration.  Then the earlier unit[] elements are fully allocated so we
can remove the checks whether "disk->queue" is NULL and the code is
simpler.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/ataflop.c

@@ -1982,6 +1982,7 @@ static int __init atari_floppy_init (void)
 							   &ataflop_mq_ops, 2,
 							   BLK_MQ_F_SHOULD_MERGE);
 		if (IS_ERR(unit[i].disk->queue)) {
+			put_disk(unit[i].disk);
 			ret = PTR_ERR(unit[i].disk->queue);
 			unit[i].disk->queue = NULL;
 			goto err;
@@ -2033,18 +2034,13 @@ static int __init atari_floppy_init (void)
 	return 0;
 
 err:
-	do {
+	while (--i >= 0) {
 		struct gendisk *disk = unit[i].disk;
 
-		if (disk) {
-			if (disk->queue) {
-				blk_cleanup_queue(disk->queue);
-				disk->queue = NULL;
-			}
-			blk_mq_free_tag_set(&unit[i].tag_set);
-			put_disk(unit[i].disk);
-		}
-	} while (i--);
+		blk_cleanup_queue(disk->queue);
+		blk_mq_free_tag_set(&unit[i].tag_set);
+		put_disk(unit[i].disk);
+	}
 
 	unregister_blkdev(FLOPPY_MAJOR, "fd");
 	return ret;