Remove hardware requirements for virtio

Gatekeeper still has two hardware requirements that the virtio driver/device doesn't support: checksumming and jumbo frames.

Jumbo frames could be made to be configurably on or off.

Checksumming will require a patch that adds software alternatives.

It's worth noting that once these hardware options are made optional, the only hardware requirement Gatekeeper has is multiqueue (for multiple TX queues per port; Gatekeeper can work with one RX queue per port since GK and GT can distribute packets to LLS, CPS, and GGU).