BugLink: http://bugs.launchpad.net/bugs/1675789

[ Upstream commit 7dcdf941 ]

Align vti6 with vti by returning GRE_KEY flag. This enables iproute2
to display tunnel keys on "ip -6 tunnel show"
Signed-off-by: David Forster <dforster@brocade.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>