Merge branch 'tipc-separate-link-and-aggregation'

Jon Maloy says:

====================
tipc: separate link and link aggregation layer

This is the first batch of a longer series that has two main objectives:

o Finer lock granularity during message sending and reception,
  especially regarding usage of the node spinlock.

o Better separation between the link layer implementation and the link
  aggregation layer, represented by node.c::struct tipc_node.

Hopefully these changes also make this part of code somewhat easier
to comprehend and maintain.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>