sandbox: correct cpu nodes

The cpu nodes in arch/sandbox/dts/test.dts should conform to the devicetree
specification:

* property device_type must be set to "cpu"
* the reg property must be provided
* the cpu nodes must have an address

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/cpu/cpu_sandbox.c b/drivers/cpu/cpu_sandbox.c
index fe6772b..2e871fe3 100644
--- a/drivers/cpu/cpu_sandbox.c
+++ b/drivers/cpu/cpu_sandbox.c
@@ -38,7 +38,7 @@
 	return 0;
 }
 
-static const char *cpu_current = "cpu-test1";
+static const char *cpu_current = "cpu@1";
 
 void cpu_sandbox_set_current(const char *name)
 {