[IPV6]: Fix behavior of ip6_route_input() for link local address

[IPV6]: Fix behavior of ip6_route_input() for link local address

I find that linux will reply echo request destined to an address which
belongs to an interface other than the one from which the request received.
This behavior doesn't make sense for link local address.

YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org> said:

Please note that sender does need to setup neighbor entry by hand to reproduce
this bug.  (Link-local address on eth1 is not visible on eth0, from the point
of view of neighbor discovery in IPv6.)

 +--------+               +--------+
 | sender |               | router |
 +---+----+               +-+----+-+
     |eth0              eth0|    |eth1
-----+----------------------+-  -+--------------

Signed-off-by: Yan Zheng <yanzheng@21cn.com>
Acked-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: Andrew Morton <akpm@osdl.org> (forwarded)
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>