ppc4xx: Fix/Update katmai board header

This patch has the following fixes/changes:

- Set 'kernel_addr' and 'ramdisk_addr' to correct values and add
  'fdt_addr' environment variable
- Remove 'kozio' environment variable
- Remove environmant variables to boot ancient arch/ppc Linux kernels
- Remove CONFIG_SYS_BOOTMAPSZ definition. It's already defined to
  the same value in amcc-common.h

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