sandbox: Add 64-bit sandbox

To debug device tree issues involving 32- and 64-bit platforms, it is useful to
have a generic 64-bit platform available.

Add a version of the sandbox that uses 64-bit integers for its physical
addresses as well as a modified device tree.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
Added CONFIG_SYS_TEXT_BASE to configs/sandbox64_defconfig
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/demo/demo-simple.c b/drivers/demo/demo-simple.c
index f069748..d05b1df 100644
--- a/drivers/demo/demo-simple.c
+++ b/drivers/demo/demo-simple.c
@@ -17,7 +17,7 @@
 {
 	const struct dm_demo_pdata *pdata = dev_get_platdata(dev);
 
-	printf("Hello from %08x: %s %d\n", map_to_sysmem(dev), pdata->colour,
+	printf("Hello from %08x: %s %d\n", (uint)map_to_sysmem(dev), pdata->colour,
 	       pdata->sides);
 
 	return 0;