tipc: refactor name table updates out of named packet receive routine

We need to perform the same actions when processing deferred name
table updates, so this functionality is moved to a separate
function.

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