powerpc: ppc4xx: remove csb272, csb472 support

These have not been converted to Generic Board, so should be removed.
(See doc/README.generic-board for details.)

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Tolunay Orkun <torkun@nextio.com>
16 files changed