tipc: tipc_disc_addr_trial_msg() can be static

Fixes: 25b0b9c4

 ("tipc: handle collisions of 32-bit node address hash values")
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>