ospfd: update some comments

* ospf_{spf,lsa}.c: remove out of date comment; add comment on some
  non-obvious code; Make note of a possible scaling problem.
diff --git a/ospfd/ospf_lsa.c b/ospfd/ospf_lsa.c
index 15a6a4c..acc9c3f 100644
--- a/ospfd/ospf_lsa.c
+++ b/ospfd/ospf_lsa.c
@@ -1528,7 +1528,10 @@
   nh.family = AF_INET;
   nh.u.prefix4 = nexthop;
   nh.prefixlen = IPV4_MAX_BITLEN;
-
+  
+  /* XXX/SCALE: If there were a lot of oi's on an ifp, then it'd be
+   * better to make use of the per-ifp table of ois.
+   */
   for (ALL_LIST_ELEMENTS_RO (ospf->oiflist, node, oi))
     if (if_is_operative (oi->ifp))
       if (oi->address->family == AF_INET)