nvme-rdma: clamp queue size according to ctrl cap

If a controller is configured with metadata support, clamp the maximal
queue size to be 128 since there are more resources that are needed
for metadata operations. Otherwise, clamp it to 256.

Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Israel Rukshin <israelr@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>