Allow setting tunnel options using the act_tunnel_key action.

Options are expressed as class:type:data and multiple options
may be listed using a comma delimiter.

 # ip link add name geneve0 type geneve dstport 0 external
 # tc qdisc add dev eth0 ingress
 # tc filter add dev eth0 protocol ip parent ffff: \
     flower indev eth0 \
        ip_proto udp \
        action tunnel_key \
            set src_ip 10.0.99.192 \
            dst_ip 10.0.99.193 \
            dst_port 6081 \
            id 11 \
            geneve_opts 0102:80:00800022,0102:80:00800022 \
    action mirred egress redirect dev geneve0

Signed-off-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>