IB/ipath: Duplicate RDMA reads can cause responder to NAK inappropriately

A duplicate RDMA read request can fool the responder into NAKing a new
RDMA read request because the responder wasn't keeping track of
whether the queue of RDMA read requests had been sent at least once.
For example, requester sends 4 2K byte RDMA read requests, times out,
and resends the first, then sees the 4 responses, then sends a 5th
RDMA read or atomic operation.  The responder sees the 4 requests,
sends 4 responses, sees the resent 1st request, rewinds the queue,
then sees the 5th request but thinks the queue is full and that the
requester is invalidly sending a 5th new request.

Signed-off-by: Ralph Campbell <ralph.campbell@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>