block: fold create_task_io_context into ioc_find_get_icq

Fold create_task_io_context into the only remaining caller.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20211209063131.18537-11-hch@lst.de


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