nfp: add set ipv4 header action flower offload

Previously we did not have offloading support for set IPv4 actions. This
patch enables TC flower offload of set IPv4 src and dst address actions.

Signed-off-by: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@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>