Documentation: add more details in tipc.rst

kernel-doc for TIPC is too simple, we need to add more information for it.

This patch is to extend the abstract, and add the Features and Links items.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>