nfp: flower: compile Geneve encap actions

Generate rules for the NFP to encapsulate packets in Geneve tunnels. Move
the vxlan action code to generic udp tunnel actions and use core code for
both vxlan and Geneve.

Only support outputting to well known port 6081. Setting tunnel options
is not supported yet.

Only attempt to offload if the fw supports Geneve.

Signed-off-by: John Hurley <john.hurley@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>