test: Make all tests depend on UNIT_TEST

Rather than having this condition defined separately for each suite,
bracket all options with 'if UNIT_TEST'.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/dm/Kconfig b/test/dm/Kconfig
index e5b341e..640421c 100644
--- a/test/dm/Kconfig
+++ b/test/dm/Kconfig
@@ -1,6 +1,6 @@
 config UT_DM
 	bool "Enable driver model unit test command"
-	depends on SANDBOX && UNIT_TEST
+	depends on SANDBOX
 	help
 	  This enables the 'ut dm' command which runs a series of unit
 	  tests on the driver model code. Each subsystem (uclass) is tested.