[IPV6]: Clean up BACKTRACK().

The fn check is unnecessary as fn can never be NULL in BACKTRACK().

Signed-off-by: Ville Nuorvala <vnuorval@tcs.hut.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index a1b0f07..263c057 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -484,7 +484,7 @@
 do { \
 	if (rt == &ip6_null_entry) { \
 		struct fib6_node *pn; \
-		while (fn) { \
+		while (1) { \
 			if (fn->fn_flags & RTN_TL_ROOT) \
 				goto out; \
 			pn = fn->parent; \