mpc8260: remove atc board support

These boards are still non-generic boards.

drivers/rtc/ds12887.c should also be removed because it can not
be built without CONFIG_ATC.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Wolfgang Denk <wd@denx.de>
diff --git a/doc/README.scrapyard b/doc/README.scrapyard
index c0d0cd9..5df0664 100644
--- a/doc/README.scrapyard
+++ b/doc/README.scrapyard
@@ -12,6 +12,7 @@
 
 Board            Arch        CPU            Commit      Removed     Last known maintainer/contact
 =================================================================================================
+atc              powerpc     mpc8260        -           -           Wolfgang Denk <wd@denx.de>
 CPU86            powerpc     mpc8260        -           -           Wolfgang Denk <wd@denx.de>
 CPU87            powerpc     mpc8260        -           -
 ep82xxm          powerpc     mpc8260        -           -