fdt: Add ft_system_setup() function for system device tree additions

Add an additional function for adding information to the device tree before
booting. This permits additions which are not board-specific.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Anatolij Gustschin <agust@denx.de>
Reviewed-by: Tom Rini <trini@ti.com>

include/image.h

@@ -119,6 +119,12 @@ struct lmb;
 # define IMAGE_OF_BOARD_SETUP		0
 #endif
 
+#ifdef CONFIG_OF_SYSTEM_SETUP
+# define IMAGE_OF_SYSTEM_SETUP	1
+#else
+# define IMAGE_OF_SYSTEM_SETUP	0
+#endif
+
 /*
  * Operating System Codes
  */