zebra: make RTF_LLINFO optional to fix FreeBSD

Signed-off-by: Lou Berger <lberger@labn.net>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/zebra/kernel_socket.c b/zebra/kernel_socket.c
index fe9e4ac..790b142 100644
--- a/zebra/kernel_socket.c
+++ b/zebra/kernel_socket.c
@@ -242,7 +242,9 @@
   {RTF_CLONING,   "CLONING"},
 #endif /* RTF_CLONING */
   {RTF_XRESOLVE,  "XRESOLVE"},
+#ifdef RTF_LLINFO
   {RTF_LLINFO,    "LLINFO"},
+#endif /* RTF_LLINFO */
   {RTF_STATIC,    "STATIC"},
   {RTF_BLACKHOLE, "BLACKHOLE"},
 #ifdef RTF_PRIVATE