This enabled multi image support for the Garz&Fricke Vincell board. Also
it adds the Vincell-LT as a second image with a separate device tree.
Previously we used the same image on both the Vincell and the Vincell-LT
image since the differences are not that significant for barebox. Still
this was good for quite some confusion internally, so let's properly
introduce a second image.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>