RDMA/rv: Public interferce for the RDMA Rendezvous module

The RDMA Rendezvous (rv) module provides an interface for HPC
middlewares to improve performance by caching memory region
registration, and improve the scalibity of RDMA transaction
through connection managements between nodes. This mechanism
is implemented through the following ioctl requests:
- ATTACH: to attach to an RDMA device.
- REG_MEM: to register a user/kernel memory region.
- DEREG_MEM: to release application use of MR, allowing it to
             remain in cache.
- GET_CACHE_STATS: to get cache statistics.
- CONN_CREATE: to create an RC connection.
- CONN_CONNECT: to start the connection.
- CONN_GET_CONN_COUNT: to use as part of error recovery from lost
                       messages in the application.
- CONN_GET_STATS: to get connection statistics.
- GET_EVENT_STATS: to get the RDMA event statistics.
- POST_RDMA_WR_IMMED: to post an RDMA WRITE WITH IMMED request.

Signed-off-by: Todd Rimmer <todd.rimmer@intel.com>
Signed-off-by: Kaike Wan <kaike.wan@intel.com>