avr32: move CONFIG_SYS_GENERIC_BOARD to Kconfig

Now all the AVR32 boards have been converted into Generic Board.
Select it in Kconfig and clean up defines in header files.

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