RDMA/cm: Delete not implemented CM peer to peer communication

Peer to peer support was never implemented, so delete it to make code less
clutter.

Link: https://lore.kernel.org/r/20200310091438.248429-6-leon@kernel.org


Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Mark Zhang <markz@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>