avr32: Kconfig: Remove pointless if around atstk1000 include

The contents of the ATSTK1000 Kconfig file itself is completely
conditional, so including it conditionally makes no sense and only adds
clutter.
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>

arch/avr32/Kconfig

@@ -121,9 +121,7 @@ config BOARD_ATNGW100
 	select CPU_AT32AP7000
 endchoice
 
-if BOARD_ATSTK1000
 source "arch/avr32/boards/atstk1000/Kconfig"
-endif
 
 choice
 	prompt "Boot loader type"