tipc: uninitialized return code in tipc_setsockopt()

We shuffled some code around and added some new case statements here and
now "res" isn't initialized on all paths.

Fixes: 01fd12bb

 ("tipc: make replicast a user selectable option")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>