ipv6: fib: Restore NTF_ROUTER exception in fib6_age()

Commit 5339ab8b (ipv6: fib: Convert fib6_age() to
dst_neigh_lookup().) seems to have mistakenly inverted the
exception for cached NTF_ROUTER routes.
Signed-off-by: NThomas Graf <tgraf@suug.ch>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/ip6_fib.c

@@ -1561,7 +1561,7 @@ static int fib6_age(struct rt6_info *rt, void *arg)
 				neigh_flags = neigh->flags;
 				neigh_release(neigh);
 			}
-			if (neigh_flags & NTF_ROUTER) {
+			if (!(neigh_flags & NTF_ROUTER)) {
 				RT6_TRACE("purging route %p via non-router but gateway\n",
 					  rt);
 				return -1;