nvme-multipath: stop using ->queuedata

nvme-multipath already uses the gendisk private data, not need to
also set up the request_queue queuedata and use it in one place only.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>