virtio-net: confusing guest offload vs features mapping

[pabeni]

After the introduction of GSO over UDP tunnel offload some virtio net features use bit > 64, but the offloads size used by VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET is 64 bits wide, the used mapping should be explicitly specified. Also we have currently conflicting definition for VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO and VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO_CSUM.

Proposed solution:

https://lore.kernel.org/virtio-comment/a30de484ff56065f56e37446e08dcdfa4850f101.1747649330.git.pabeni@redhat.com/T/#u