bgpd: compile warnings cleanup

* bgpd/bgp_fsm.c
  * bgp_clearing_completed(): only used in one file, can be static
* bgpd/bgp_packet.c
  * afi2str(): sayonara
  * safi2str(): sayonara
* bgpd/bgp_route.c
  * bgp_distance_reset(): sayonara
* bgpd/bgp_zebra.c
  * bgp_ifindex_by_nexthop(): sayonara
diff --git a/bgpd/bgp_fsm.c b/bgpd/bgp_fsm.c
index 6121e74..c815f9a 100644
--- a/bgpd/bgp_fsm.c
+++ b/bgpd/bgp_fsm.c
@@ -427,7 +427,7 @@
 }
 
 /* Flush the event queue and ensure the peer is shut down */
-int
+static int
 bgp_clearing_completed (struct peer *peer)
 {
   int rc = bgp_stop(peer);