Commit "virtio-rng: support multiple virtio-rng devices" has broken
boot with a virtio-rng device because the 'init' callback of the
virtio-rng device was left unitialized to garbage, and got called
by the hwrng infrastructure, killing the guest on boot.
Signed-off-by: Sasha Levin <firstname.lastname@example.org>
Signed-off-by: Rusty Russell <email@example.com>