block: Error an attempt to split an atomic write in bio_split()

This is disallowed.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20241111112150.3756529-3-john.g.garry@oracle.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>