tipc: Return non-zero value from tipc_udp_addr2str() on error

tipc_udp_addr2str() should return non-zero value if the UDP media
address is invalid. Otherwise, a buffer overflow access can occur in
tipc_media_addr_printf(). Fix this by returning 1 on an invalid UDP
media address.

Fixes: d0f91938

 ("tipc: add ip/udp media type")
Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
Reviewed-by: Tung Nguyen <tung.q.nguyen@endava.com>
Signed-off-by: David S. Miller <davem@davemloft.net>