nfp: flower: ignore checksum actions when performing pedit actions

Hardware will automatically update csum in headers when a set action has
been performed. This means we could in the driver ignore the explicit
checksum action when performing a set action.

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