RDMA/efa: Add EFA verbs implementation

Add a file that implements the EFA verbs.
Signed-off-by: NGal Pressman <galpress@amazon.com>
Reviewed-by: NShiraz Saleem <shiraz.saleem@intel.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>