tipc: Let tipc_release() return 0

net/tipc/socket.c: In function ‘tipc_release’:
net/tipc/socket.c:352: warning: ‘res’ is used uninitialized in this function

Introduced by commit 24be34b5 ("tipc:
eliminate upcall function pointers between port and socket"), which
removed the sole initializer of "res".

Just return 0 to fix it.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: David S. Miller <davem@davemloft.net>