README.scrapyard: add entries for dead board, T4240EMU and sc3

Follow-up commit 7fc63cca611b (mpc85xx/T4240EMU: Remove T4240EMU
board), and commit 27e721564591 (ppc4xx: Remove sc3 board),
filling the blank fields.

Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
1 file changed