blk-mq: remove blk_flush_queue_rq

Just call blk_mq_add_to_requeue_list directly from the two callers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20230413064057.707578-10-hch@lst.de


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