The BINARY files given in the config files are expected to be relative
to the place kwbimage is called from. This is bad since it breaks where
kwbimage is called from the build directory and not the source
directory.
It makes more sense to make the paths in the config files relative
to the config files which works with out of tree builds and is also
more what a user normally expects.

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

This converts Marvell Armada XP based PlatHome Openblocks AX3-4
to PBL_MULTI_IMAGES. A DT overlay is added to keep possible
barebox-specific changes separated and added to lowlevel
board init.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>

The OpenBlocks AX3 platform is manufactured by PlatHome and uses the
MV78260 dual-core SoC from the Armada XP family.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Tested-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>