nvmet-rdma: set max_queue_size for RDMA transport

A new port configuration was added to set max_queue_size. Clamp user
configuration to RDMA transport limits.

Increase the maximal queue size of RDMA controllers from 128 to 256
(the default size stays 128 same as before).

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