IB/iser: Fix responder resources advertisement

The iser initiator is the RDMA responder so it should publish to the
target the max inflight rdma read requests its local HCA can handle in
responder_resources (max_qp_rd_atom).

The iser target should take the min of that and its local HCA max
inflight oustanding rdma read requests (max_qp_init_rd_atom).

We keep initiator_depth set to 1 in order to compat with old targets.

Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>