tipc: tipc_node_create() can be static

Fixes the following sparse warning:

net/tipc/node.c:336:18: warning:
 symbol 'tipc_node_create' was not declared. Should it be static?

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>