[cleanup] functions taking no args should be declared with void args

Use Ansi-C prototypes rather than old K&R method of declaring
function without arguments
diff --git a/ospfd/ospf_snmp.c b/ospfd/ospf_snmp.c
index 5a0aea1..cc4974c 100644
--- a/ospfd/ospf_snmp.c
+++ b/ospfd/ospf_snmp.c
@@ -1403,7 +1403,7 @@
 };
 
 static struct ospf_snmp_if *
-ospf_snmp_if_new ()
+ospf_snmp_if_new (void)
 {
   return XCALLOC (0, sizeof (struct ospf_snmp_if));
 }