virtio: add API for VIRTIO devices and add VIRTIO PCI driver

This commit adds the API for accessing VIRTIO devices, and adds a driver
for a VIRTIO PCIE device based on the newly added API.

This commit is based on the Virtual I/O Device (VIRTIO) Version 1.3
specification:
https://docs.oasis-open.org/virtio/virtio/v1.3/csd01/virtio-v1.3-csd01.pdf



Signed-off-by: Jakub Michalski <jmichalski@antmicro.com>
Signed-off-by: Filip Kokosinski <fkokosinski@antmicro.com>