nfp: add IPv6 ttl and tos match offloading support

Previously matching on IPv6 ttl and tos fields were not offloaded. This
patch enables offloading IPv6 ttl and tos as match fields.

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>