*: fix more initialisers (for BSD)

FreeBSD and NetBSD spew a few more warnings about variable initialisers.
Found with OSR's/NetDEF's fancy new CI system.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/bgpd/bgp_routemap.c b/bgpd/bgp_routemap.c
index 33f802c..416a3e5 100644
--- a/bgpd/bgp_routemap.c
+++ b/bgpd/bgp_routemap.c
@@ -131,8 +131,8 @@
       void *object)
 {
   union sockunion *su;
-  union sockunion su_def = { .sin.sin_family = AF_INET,
-			     .sin.sin_addr.s_addr = INADDR_ANY };
+  union sockunion su_def = { .sin = { .sin_family = AF_INET,
+                                      .sin_addr.s_addr = INADDR_ANY } };
   struct peer_group *group;
   struct peer *peer;
   struct listnode *node, *nnode;