sandbox: implement ft_board_setup()

Currently we are not able to test reservations created by ft_board_setup().

Implement ft_board_setup() to create an arbitrary reservation and enable
OF_BOARD_SETUP.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromum.org>
diff --git a/arch/Kconfig b/arch/Kconfig
index ae9c93e..91e049b 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -96,6 +96,7 @@
 	select DM_SPI_FLASH
 	select HAVE_BLOCK_DEVICE
 	select LZO
+	select OF_BOARD_SETUP
 	select PCI_ENDPOINT
 	select SPI
 	select SUPPORT_OF_CONTROL