RDMA: Move rdma_node_type to uapi/

This enum is exposed over the sysfs file 'node_type' and over netlink via
RDMA_NLDEV_ATTR_DEV_NODE_TYPE, so declare it in the uapi headers.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>