nfp: add flower app

Add app for flower offload. At this point the PF netdev and phys port
representor netdevs are initialised. Follow-up work will add support for
VF and PF representors and beyond that offloading the flower classifier.

Based in part on work by Benjamin LaHaise and Bert van Leeuwen.

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