dm: test: Add a Kconfig file

Add a file to control driver model test features.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/test/dm/Kconfig b/test/dm/Kconfig
new file mode 100644
index 0000000..a9d0298
--- /dev/null
+++ b/test/dm/Kconfig
@@ -0,0 +1,8 @@
+config DM_TEST
+	bool "Enable driver model test command"
+	depends on SANDBOX && CMD_DM
+	help
+	  This enables the 'dm test' command which runs a series of unit
+	  tests on the driver model code. Each subsystem (uclass) is tested.
+	  If all is well then all tests pass although there will be a few
+	  messages printed along the way.