[POWERPC] 4xx: Add AMCC Kilauea eval board support to platforms/40x

This patch adds basic support for the new 405EX and the AMCC eval board
Kilauea to arch/powerpc.

Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>