Add virtio-net driver

[vinc]

• https://ozlabs.org/~rusty/virtio-spec/virtio-0.9.5.pdf
• https://docs.oasis-open.org/virtio/virtio/v1.0/virtio-v1.0.html

[vinc]

Getting the MAC address:

Now the next step is to build the virtqueue which is a bit harder due to memory requirements...