RDMA/netlink: Add netlink device definitions to UAPI

RDMA/netlink: Add netlink device definitions to UAPI

Introduce new defines to rdma_netlink.h, so the RDMA configuration tool
will be able to communicate with RDMA subsystem by using the shared defines.

The addition of new client (NLDEV) revealed the fact that we exposed by
mistake the RDMA_NL_I40IW define which is not backed by any RDMA netlink
by now and it won't be exposed in the future too. So this patch reuses
the value and deletes the old defines.

The NLDEV operates with objects. The struct ib_device has two straightforward
objects: device itself and ports of that device.

This brings us to propose the following commands to work on those objects:
 * RDMA_NLDEV_CMD_{GET,SET,NEW,DEL} - works on ib_device itself
 * RDMA_NLDEV_CMD_PORT_{GET,SET,NEW,DEL} - works on ports of specific ib_device

Those commands receive/return the device index (RDMA_NLDEV_ATTR_DEV_INDEX)
and port index (RDMA_NLDEV_ATTR_PORT_INDEX). For device object accesses,
the RDMA_NLDEV_ATTR_PORT_INDEX will return the maximum number of ports
for specific ib_device and for port access the actual port index.

The port index starts from 1 to follow RDMA/core internal semantics and
the sysfs exposed knobs.

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Steve Wise <swise@opengridcomputing.com>