powerpc: adder: remove orphan board

This board has been orphan for a while.
(Emails to its maintainer have been bouncing.)

Because MPC8xx family is old enough, nobody would pick up
the maintainership on it.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Wolfgang Denx <wd@denx.de>
diff --git a/doc/README.scrapyard b/doc/README.scrapyard
index 49cb4ca..fac4199 100644
--- a/doc/README.scrapyard
+++ b/doc/README.scrapyard
@@ -11,6 +11,7 @@
 
 Board            Arch        CPU            Commit      Removed     Last known maintainer/contact
 =================================================================================================
+adder            powerpc     mpc8xx         -           -           Yuli Barcohen <yuli@arabellasw.com>
 quad100hd	 powerpc     ppc405ep	    -		-	    Gary Jennejohn <gljennjohn@googlemail.com>
 lubbock          arm         pxa            36bf57b     2014-04-18  Kyle Harris <kharris@nexus-tech.net>
 EVB64260	 powerpc     mpc824x        bb3aef9	2014-04-18