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/arch/sandbox/dts/Makefile b/arch/sandbox/dts/Makefile
index 0197569..861b4dc 100644
--- a/arch/sandbox/dts/Makefile
+++ b/arch/sandbox/dts/Makefile
@@ -2,7 +2,11 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
+ifdef CONFIG_SANDBOX64
+dtb-$(CONFIG_SANDBOX) += sandbox64.dtb
+else
 dtb-$(CONFIG_SANDBOX) += sandbox.dtb
+endif
 dtb-$(CONFIG_UT_DM) += test.dtb
 
 targets += $(dtb-y)