tipc: Eliminate use of user registry by topology service

Simplifies TIPC's network topology service so that it no longer registers
its ports with the user registry, since the service doesn't take advantage
of any of the registry's capabilities.

Signed-off-by: Allan Stephens <Allan.Stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>