tipc: Remove prototype code for supporting slave nodes

Simplifies routines and data structures that were intended to allow
TIPC to support slave nodes (i.e. nodes that did not have links to
all of the other nodes in its cluster, forcing TIPC to route messages
that it could not deliver directly through a non-slave node).

Currently, TIPC supports only networks containing non-slave nodes,
so this code is unnecessary.

Note: The latest edition of the TIPC 2.0 Specification has eliminated
the concept of slave nodes entirely.

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>