RDMA/cma: Add support for netlink statistics export
Add callbacks and data types for statistics export of all current
devices/ids. The schema for RDMA CM is a series of netlink messages.
Each one contains an rdma_cm_stat struct. Additionally, two netlink
attributes are created for the addresses for each message (if
applicable).
Their types used are:
RDMA_NL_RDMA_CM_ATTR_SRC_ADDR (The source address for this ID)
RDMA_NL_RDMA_CM_ATTR_DST_ADDR (The destination address for this ID)
sockaddr_* structs are encapsulated within these attributes.
In other words, every transaction contains a series of messages like: