net/mlx5: Fix checksum issue of VXLAN and IPsec crypto offload

The packet is VXLAN packet over IPsec transport mode tunnel
which has the following format: [IP1 | ESP | UDP | VXLAN | IP2 | TCP]
NVIDIA ConnectX card cannot do checksum offload for two L4 headers.
The solution is using the checksum partial offload similar to
VXLAN | TCP packet. Hardware calculates IP1, IP2 and TCP checksums and
software calculates UDP checksum. However, unlike VXLAN | TCP case,
IPsec's mlx5 driver cannot access the inner plaintext IP protocol type.
Therefore, inner_ipproto is added in the sec_path structure
to provide this information. Also, utilize the skb's csum_start to
program L4 inner checksum offset.

While at it, remove the call to mlx5e_set_eseg_swp and setup software parser
fields directly in mlx5e_ipsec_set_swp. mlx5e_set_eseg_swp is not
needed as the two features (GENEVE and IPsec) are different and adding
this sharing layer creates unnecessary complexity and affect
performance.

For the case VXLAN packet over IPsec tunnel mode tunnel, checksum offload
is disabled because the hardware does not support checksum offload for
three L3 (IP) headers.

Signed-off-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Huy Nguyen <huyn@nvidia.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>