tipc: add policy for TIPC_NLA_NET_ADDR

Before syzbot/KMSAN bites, add the missing policy for TIPC_NLA_NET_ADDR

Fixes: 27c21416 ("tipc: add net set to new netlink api")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jon Maloy <jon.maloy@ericsson.com>
Cc: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>