tipc: remove node subscription infrastructure

The node subscribe infrastructure represents a virtual base class, so
its users, such as struct tipc_port and struct publication, can derive
its implemented functionalities. However, after the removal of struct
tipc_port, struct publication is left as its only single user now. So
defining an abstract infrastructure for one user becomes no longer
reasonable. If corresponding new functions associated with the
infrastructure are moved to name_table.c file, the node subscription
infrastructure can be removed as well.

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>