With imd we can store metadata in barebox images. Let's use this
information to further verify that the image that is to be flashed
is the correct one. This patch extracts the device tree compatible
from the image and compares it with the one from the currently
running barebox. If it doesn't match the update is aborted with a
warning.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>