dm: Add a 'dm' command for testing

This command is not required for driver model operation, but can be useful
for testing. It provides simple dumps of internal data structures.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Pavel Herrmann <morpheus.ibis@gmail.com>
Signed-off-by: Viktor Křivák <viktor.krivak@gmail.com>
Signed-off-by: Tomas Hlavacek <tmshlvck@gmail.com>
diff --git a/include/configs/sandbox.h b/include/configs/sandbox.h
index c9c8509..8e034a7 100644
--- a/include/configs/sandbox.h
+++ b/include/configs/sandbox.h
@@ -21,6 +21,7 @@
 #define CONFIG_BOOTSTAGE
 #define CONFIG_BOOTSTAGE_REPORT
 #define CONFIG_DM
+#define CONFIG_CMD_DM
 #define CONFIG_DM_TEST
 
 /* Number of bits in a C 'long' on this architecture */