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>

Kconfig

@@ -166,3 +166,5 @@ source "drivers/Kconfig"
 source "fs/Kconfig"
 
 source "lib/Kconfig"
+
+source "test/Kconfig"

test/Kconfig

+source "test/dm/Kconfig"

test/dm/Kconfig

+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.