Add a sanity check to del_gendisk to do nothing when the disk wasn't
successfully added.  This papers over the complete lack of add_disk
error handling, which is about to get fixed gradually.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210818144542.19305-2-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>