ip6_tunnel: fix traffic class routing for tunnels

ip6_tunnel: fix traffic class routing for tunnels

[ Upstream commit 5f733ee68f9a4df94775299ac6a7ab260704f6ed ]

ip6_route_output() requires that the flowlabel contains the traffic
class for policy routing.

Commit 0e9a709560db ("ip6_tunnel, ip6_gre: fix setting of DSCP on
encapsulated packets") removed the code which previously added the
traffic class to the flowlabel.

The traffic class is added here because only route lookup needs the
flowlabel to contain the traffic class.

Fixes: 0e9a709560db ("ip6_tunnel, ip6_gre: fix setting of DSCP on encapsulated packets")
Signed-off-by: Liam McBirnie <liam.mcbirnie@boeing.com>
Acked-by: Peter Dawson <peter.a.dawson@boeing.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>