nvme-rdma: don't override opts->queue_size

That is user argument, and theoretically controller limits can change
over time (over reconnects/resets).  Instead, use the sqsize controller
attribute to check queue depth boundaries and use it to the tagset
allocation.

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>