ppc4xx: Update Kilauea defconfig to use device-tree booting as default

This patch reworks the default environment on Kilauea/Haleakala. Now
"net_nfs" for exmaple uses the device-tree style booting formerly know
as "net_nfs_fdt". Also the addresses in RAM were changed because of the
new image booting support, which check for image overwriting. So the
addresses needed togeet adjusted.

Signed-off-by: Stefan Roese <sr@denx.de>