nfp: fix incorrectly set csum flag for nfd3 path

The csum flag of IPsec packet are set repeatedly. Therefore, the csum
flag set of IPsec and non-IPsec packet need to be distinguished.

As the ipv6 header does not have a csum field, so l3-csum flag is not
required to be set for ipv6 case.

L4-csum flag include the tcp csum flag and udp csum flag, we shouldn't
set the udp and tcp csum flag at the same time for one packet, should
set l4-csum flag according to the transport layer is tcp or udp.

Fixes: 57f273adbcd4 ("nfp: add framework to support ipsec offloading")
Signed-off-by: Huanhuan Wang <huanhuan.wang@corigine.com>
Reviewed-by: Louis Peens <louis.peens@corigine.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

nfp: add framework to support ipsec offloading

A new metadata type and config structure are introduced to
interact with firmware to support ipsec offloading. This
feature relies on specific firmware that supports ipsec
encrypt/decrypt by advertising related capability bit.

The xfrm callbacks which interact with upper layer are
implemented in the following patch.

Based on initial work of Norm Bagley <norman.bagley@netronome.com>.

Signed-off-by: Huanhuan Wang <huanhuan.wang@corigine.com>
Reviewed-by: Louis Peens <louis.peens@corigine.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>