RDMA/nldev: Provide detailed QP information

Implement RDMA nldev netlink interface to get detailed information on each
QP in the system. This includes the owning process or kernel ULP and
detailed information from the qp_attrs.

Currently only the dumpit variant is implemented.

Reviewed-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>