[cleanup] Convert XMALLOC/memset to XCALLOC

Simple conversion of XMALLOC/memset to XCALLOC
diff --git a/ripngd/ripngd.c b/ripngd/ripngd.c
index 5e9bfc5..7b00e03 100644
--- a/ripngd/ripngd.c
+++ b/ripngd/ripngd.c
@@ -1820,8 +1820,7 @@
   assert (ripng == NULL);
 
   /* Allocaste RIPng instance. */
-  ripng = XMALLOC (MTYPE_RIPNG, sizeof (struct ripng));
-  memset (ripng, 0, sizeof (struct ripng));
+  ripng = XCALLOC (MTYPE_RIPNG, sizeof (struct ripng));
 
   /* Default version and timer values. */
   ripng->version = RIPNG_V1;