[POWERPC] bootwrapper: Add a cuboot platform and a cuImage target

The cuImage target will build a uImage with bootwrapper code and a device
tree.  The default device tree and platform file are determined by the
kernel configuration.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
4 files changed