[IPv6] route: Simplify ip6_del_rt()

Provide a simple ip6_del_rt() for the majority of users and
an alternative for the exception via netlink. Avoids code
obfuscation.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 5743e8b..419d651 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -961,7 +961,7 @@
 			struct rt6_info *rt;
 			rt = rt6_get_dflt_router(saddr, dev);
 			if (rt)
-				ip6_del_rt(rt, NULL, NULL, NULL);
+				ip6_del_rt(rt);
 		}
 
 out:
@@ -1114,7 +1114,7 @@
 
 	if (rt && lifetime == 0) {
 		neigh_clone(neigh);
-		ip6_del_rt(rt, NULL, NULL, NULL);
+		ip6_del_rt(rt);
 		rt = NULL;
 	}