[cleanup] Convert XMALLOC/memset to XCALLOC

Simple conversion of XMALLOC/memset to XCALLOC
diff --git a/ripd/rip_interface.c b/ripd/rip_interface.c
index 7c5577b..54d357c 100644
--- a/ripd/rip_interface.c
+++ b/ripd/rip_interface.c
@@ -118,8 +118,7 @@
 {
   struct rip_interface *ri;
 
-  ri = XMALLOC (MTYPE_RIP_INTERFACE, sizeof (struct rip_interface));
-  memset (ri, 0, sizeof (struct rip_interface));
+  ri = XCALLOC (MTYPE_RIP_INTERFACE, sizeof (struct rip_interface));
 
   /* Default authentication type is simple password for Cisco
      compatibility. */