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>
diff --git a/doc/README.scrapyard b/doc/README.scrapyard
index cdb2b6e..87e2b35 100644
--- a/doc/README.scrapyard
+++ b/doc/README.scrapyard
@@ -12,6 +12,7 @@
 
 Board            Arch        CPU            Commit      Removed     Last known maintainer/contact
 =================================================================================================
+csb272/csb472    powerpc     ppc4xx         -           -           Tolunay Orkun <torkun@nextio.com>
 alpr             powerpc     ppc4xx         -           -           Stefan Roese <sr@denx.de>
 cam_enc_4xx      arm         arm926ejs      8d775763    2015-08-20  Heiko Schocher <hs@denx.de>
 atstk1003        avr32       -              e5354b8a    2015-06-10  Haavard Skinnemoen <haavard.skinnemoen@atmel.com>