powerpc: mpc85xx: remove stxgp3, stxssa 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: Dan Malek <dan@embeddedalley.com>
diff --git a/doc/README.scrapyard b/doc/README.scrapyard
index d97e82f..9cda0bd 100644
--- a/doc/README.scrapyard
+++ b/doc/README.scrapyard
@@ -12,6 +12,8 @@
 
 Board            Arch        CPU            Commit      Removed     Last known maintainer/contact
 =================================================================================================
+stxgp3           powerpc     mpc85xx        -           -           Dan Malek <dan@embeddedalley.com>
+stxssa           powerpc     mpc85xx        -           -           Dan Malek <dan@embeddedalley.com>
 cmi_mpc5xx       powerpc     mpc5xx         -           -
 zeus             powerpc     ppc4xx         -           -           Stefan Roese <sr@denx.de>
 sbc405           powerpc     ppc4xx         -           -