ppc: Add support for AMCC 440SPe Katmai board

This series of patches adds support for the AMCC Katmai evaluation board based on the 440SPe. It's still arch/ppc, so likely no chance of merging upstream. Mainly for completeness. When the 4xx support in arch/powerpc has stabilized a little we will try to move this support to arch/powerpc too.

Best regards,
Stefan