OS-2366 ddi_periodic_add(9F) is entirely rubbish

@@ -19,10 +19,11 @@
 # CDDL HEADER END
 #
 #
 # Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
 # Copyright (c) 1999, 2010, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2013, Joyent, Inc.  All rights reserved.
 #
 
 #
 # This file simply contains the list of sources files compiled together
 # to create the genunix mdb module.   Having them in one place saves

@@ -37,10 +38,11 @@
         cpupart.c       \
         cred.c          \
         ctxop.c         \
         cyclic.c        \
         damap.c         \
+        ddi_periodic.c  \
         devinfo.c       \
         dist.c          \
         findstack.c     \
         findstack_subr.c \
         fm.c            \