When the VIRTIO device doesn't report a MAC in config space,
generate a random locally-administered unicast MAC instead of
panicking with unimplemented!(). This matches Linux 7.1
drivers/net/virtio_net.c virtnet_probe() behavior.
Reads /scheme/rand for random bytes; falls back to a fixed
MAC if the random source is unavailable. MAC is forced to
unicast + locally administered (bit 0=0, bit 1=1).
Red Bear OS