ospfd: Update nsm_change_state to static scope, as it is not called from elsewhere

Signed-off-by: Scott Feldman <sfeldma@cumulusnetworks.com>
diff --git a/ospfd/ospf_nsm.c b/ospfd/ospf_nsm.c
index cbc3171..436896c 100644
--- a/ospfd/ospf_nsm.c
+++ b/ospfd/ospf_nsm.c
@@ -643,7 +643,7 @@
 #endif
 }
 
-void
+static void
 nsm_change_state (struct ospf_neighbor *nbr, int state)
 {
   struct ospf_interface *oi = nbr->oi;