net/mlx5e: Fix IPv6 tunnel checksum offload

The mlx5 driver exposes support for TSO6 but not IPv6 csum for hardware
encapsulated tunnels.  This leads to issues as it triggers warnings in
skb_checksum_help as it ends up being called as we report supporting the
segmentation but not the checksumming for IPv6 frames.

This patch corrects that and drops 2 features that don't actually need to
be supported in hw_enc_features since they are Rx features and don't
actually impact anything by being present in hw_enc_features.

Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>