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>
diff --git a/arch/Kconfig b/arch/Kconfig
index 200588a..96db5c5 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -25,6 +25,7 @@
 config AVR32
 	bool "AVR32 architecture"
 	select HAVE_GENERIC_BOARD
+	select SYS_GENERIC_BOARD
 
 config BLACKFIN
 	bool "Blackfin architecture"