README.scrapyard: add entries for dead AVR32 boards

Some AVR32 boards were dropped by the following commits:
 9eb45aabe078 (avr32: delete non generic board favr-32-ezkit)
 e36930764471 (avr32: delete non generic board hammerhead)
 c62d2f8fc5c6 (avr32: delete non generic board mimc200)
 e5354b8a9e2a (avr32: delete non generic board's atstk100{3, 4, 6})

Acked-by: Andreas Bießmann <andreas.devel@googlemail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
1 file changed