RDMA: iWARP Connection Manager.

Add an iWARP Connection Manager (CM), which abstracts connection
management for iWARP devices (RNICs).  It is a logical instance of the
xx_cm where xx is the transport type (ib or iw).  The symbols exported
are used by the transport independent rdma_cm module, and are
available also for transport dependent ULPs.

Signed-off-by: Tom Tucker <tom@opengridcomputing.com>
Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>