In addition to the real on-link routes, NONEXTHOP routes
should be considered on-link.

Problem reported by Meelis Roos <mroos@linux.ee>.
Signed-off-by: NYOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Acked-by: NMeelis Roos <mroos@linux.ee>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>