Changes

route: osmo_ss7_route_name(): Use osmo_ss7_pointcode_print_buf()

This allows callers to call osmo_ss7_route_name() together with
osmo_ss7_pointcode_print() and osmo_ss7_pointcode_print2() in the same
LOG line.

Change-Id: Iccbd83eeaa0e1c2a6078ece8d5c6d7af6fd9d71a