powerpc: remove RPXsuper board support

Enough time has passed since this board was moved to Orphan. Remove.

 - Remove board/rpxsuper/*
 - Remove include/configs/RPXsuper.h
 - Move the entry from boards.cfg to doc/README.scrapyard

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/doc/README.scrapyard b/doc/README.scrapyard
index 9915500..125ba80 100644
--- a/doc/README.scrapyard
+++ b/doc/README.scrapyard
@@ -11,6 +11,7 @@
 
 Board            Arch        CPU            Commit      Removed     Last known maintainer/contact
 =================================================================================================
+RPXsuper         powerpc     mpc8260        -           2014-04-04
 RPXClassic       powerpc     mpc8xx         -           2014-04-04
 RPXlite          powerpc     mpc8xx         -           2014-04-04
 genietv          powerpc     mpc8xx         -           2014-04-04