nfp: add set ipv6 source and destination address

Previously we did not have offloading support for set IPv6 actions. This
patch enables TC flower offload of set IPv6 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>