Zap unused ND6_IS_LLINFO_PROBREACH and MAX_REACHABLE_TIME

[Klemens Nanni]

Leftovers from florian's RS/NA purge from the kernel in 2017.

OK?

diff --git a/sys/netinet6/nd6.h b/sys/netinet6/nd6.h
index 82e674c5ecf..01ec60d02b9 100644
--- a/sys/netinet6/nd6.h
+++ b/sys/netinet6/nd6.h
@@ -109,11 +109,9 @@ struct     llinfo_nd6 {
        short   ln_router;      /* 2^0: ND6 router bit */
 };
 
-#define ND6_IS_LLINFO_PROBREACH(n) ((n)->ln_state > ND6_LLINFO_INCOMPLETE)
 #define ND6_LLINFO_PERMANENT(n)        ((n)->ln_rt->rt_expire == 0)
 
 /* node constants */
-#define MAX_REACHABLE_TIME             3600000 /* msec */
 #define REACHABLE_TIME                 30000   /* msec */
 #define RETRANS_TIMER                  1000    /* msec */
 #define MIN_RANDOM_FACTOR              512     /* 1024 * 0.5 */