powerpc: remove cogent_8xx, cogent_mpc8260 board support

These boards are still non-generic boards.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Murray Jensen <Murray.Jensen@csiro.au>
diff --git a/doc/README.scrapyard b/doc/README.scrapyard
index 9d6a6b6..c9b4b17 100644
--- a/doc/README.scrapyard
+++ b/doc/README.scrapyard
@@ -12,6 +12,8 @@
 
 Board            Arch        CPU            Commit      Removed     Last known maintainer/contact
 =================================================================================================
+cogent_mpc8260   powerpc     mpc8260        -           -           Murray Jensen <Murray.Jensen@csiro.au>
+cogent_8xx       powerpc     mpc8xx         -           -           Murray Jensen <Murray.Jensen@csiro.au>
 ESTEEM192E       powerpc     mpc8xx         -           -           Conn Clark <clark@esteem.com>
 IP860            powerpc     mpc8xx         -           -           Wolfgang Denk <wd@denx.de>
 IVML24           powerpc     mpc8xx         -           -           Wolfgang Denk <wd@denx.de>