vbe: Add info about the VBE device to the fwupd node

vbe: Add info about the VBE device to the fwupd node

At present we put the driver in the /chosen node in U-Boot. This is a bit
strange, since U-Boot doesn't normally use that node itself. It is better
to put it under the bootstd node.

To make this work we need to copy create the node under /chosen when
fixing up the device tree. Copy over all the properties so that fwupd
knows what to do.

Update the sandbox device tree accordingly.

Signed-off-by: Simon Glass <sjg@chromium.org>