Revert "hw/net/virtio-net: make VirtIONet.vlans an array instead of a pointer"

Revert "hw/net/virtio-net: make VirtIONet.vlans an array instead of a pointer"

Per https://lore.kernel.org/qemu-devel/7798584d-e861-47b7-af52-2c2efb67a4de@proxmox.com/:

Loading a VM state taken with v10.1.2 or older doesn't work anymore,
using the script [*] we get:

  kvm: VQ 1 size 0x100 < last_avail_idx 0x9 - used_idx 0x3e30
  kvm: load of migration failed: Operation not permitted: error while loading state for instance 0x0 of device '0000:00:13.0/virtio-net': Failed to load element of type virtio for virtio: -1
  qemu-system-x86_64: Missing section footer for 0000:00:13.0/virtio-net
  qemu-system-x86_64: Section footer error, section_id: 41

[*]:

  #!/bin/bash
  rm /tmp/disk.qcow2
  args="
    -netdev type=tap,id=net1,ifname=tap104i1,script=/usr/libexec/qemu-server/pve-bridge,downscript=/usr/libexec/qemu-server/pve-bridgedown,vhost=on
    -device virtio-net-pci,mac=BC:24:11:32:3C:69,netdev=net1,bus=pci.0,addr=0x13,id=net1
    -machine type=pc-i440fx-10.1
  "
  $1/qemu-img create -f qcow2 /tmp/disk.qcow2 1G
  $1/qemu-system-x86_64 --qmp stdio --blockdev qcow2,node-name=node0,file.driver=file,file.filename=/tmp/disk.qcow2 $args <<EOF
  {"execute": "qmp_capabilities"}
  {"execute": "snapshot-save", "arguments": { "job-id": "save0", "tag": "snap", "vmstate": "node0", "devices": ["node0"] } }
  {"execute": "quit"}
  EOF
  $2/qemu-system-x86_64 --qmp stdio --blockdev qcow2,node-name=node0,file.driver=file,file.filename=/tmp/disk.qcow2 $args -loadvm snap

This reverts commit 3a9cd2a4a1571266dea37398de04f650c2a72d86.

Reported-by: Fiona Ebner <f.ebner@proxmox.com>
Suggested-by: Fiona Ebner <f.ebner@proxmox.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>