[ofw] librdmacm.dll PD

[Sean Hefty]

>The current implementation of rdma_cm makes it necessary for PD to be
>allocated for every connection. But I think underlaying  WinVerbs can
>support single PD across multiple connections for a given IB device.
>Please let me know if I am correct.

You can allocate a single PD and use it for multiple connections as long as the
corresponding rdma_cm_id's all reference the same device.  The librdmacm
maintains a single device list, which is only freed once the user releases all
references to it. 

- Sean