net/ipv6/tcp_ipv6.c: Use compressed IPv6 address

Use "[compressed ipv6]:port" form suggested by:
http://tools.ietf.org/id/draft-ietf-6man-text-addr-representation-03.txt



Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>