tipc: fix error handling in tipc_udp_enable()

Release alloced resource before return from the error handling
case in tipc_udp_enable(), otherwise will cause memory leak.

Fixes: 52dfae5c ("tipc: obtain node identity from interface by default")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>