[cleanup] Convert XMALLOC/memset to XCALLOC

Simple conversion of XMALLOC/memset to XCALLOC
diff --git a/ospf6d/ospf6_top.c b/ospf6d/ospf6_top.c
index f59b6f9..d45d132 100644
--- a/ospf6d/ospf6_top.c
+++ b/ospf6d/ospf6_top.c
@@ -114,8 +114,7 @@
 {
   struct ospf6 *o;
 
-  o = XMALLOC (MTYPE_OSPF6_TOP, sizeof (struct ospf6));
-  memset (o, 0, sizeof (struct ospf6));
+  o = XCALLOC (MTYPE_OSPF6_TOP, sizeof (struct ospf6));
 
   /* initialize */
   gettimeofday (&o->starttime, (struct timezone *) NULL);