virtio-blk: Fix memory leak among suspend/resume procedure

The vblk->vqs should be freed before we call init_vqs()
in virtblk_restore().

Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Link: https://lore.kernel.org/r/20210517084332.280-1-xieyongji@bytedance.com
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>