ppc4xx: Fix missing linker scripts for partial linking

This patch fixes the acadia_nand and kilauea_nand linker scripts
which have been missing in commit ee8028b7 [ppc4xx: Cleanup for
partial linking and --gc-sections]

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Bernhard Weirich <Bernhard.Weirich@riedel.net>