OvmfPkg: VirtioRngDxe: adapt feature negotiation to virtio-1.0
Relative to virtio-0.9.5, virtio-1.0 reverses the order of queue discovery
and feature negotiation. In virtio-1.0, feature negotiation has to
complete first, and the device can also reject a self-inconsistent feature
request through the new VSTAT_FEATURES_OK status bit. (For example if the
driver requests a higher level feature but clears a prerequisite feature.)
Furthermore, we retain the VIRTIO_F_VERSION_1 feature bit if the
VIRTIO_DEVICE_PROTOCOL provider has high enough revision.