virtio: move dev_to_virtio() to use container_of_const()

The driver core is changing to pass some pointers as const, so move
dev_to_virtio() to use container_of_const() to handle this change.

dev_to_virtio() now properly keeps the const-ness of the pointer passed
into it, while as before it could be lost.

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20230111113018.459199-12-gregkh@linuxfoundation.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>