[IPV6] HASHTABLES: Use appropriate seed for caluculating ehash index.

Tetsuo Handa <handat@pm.nttdata.co.jp> told me that connect(2) with TCPv6
socket almost always took a few minutes to return when we did not have any
ports available in the range of net.ipv4.ip_local_port_range.

The reason was that we used incorrect seed for calculating index of
hash when we check established sockets in __inet6_check_established().

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Adrian Bunk <bunk@stusta.de>