ipv6: fix display of local and remote sit endpoints

This fixes the regressions cause by
commit 1326c3d5


(v2.6.28-rc6-461-g23a12b1) broke the display of local and remote
addresses of an SIT tunnel in iproute2.

nt->parms is used by ipip6_tunnel_init() and therefore need to be
initialized first.

Tracked as http://bugzilla.kernel.org/show_bug.cgi?id=12868

Reported-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>