test: dm: Move the dm tests over to the ut command

Unify the command for running unit tests further by moving the "dm test"
command over to "ut dm".

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/sandbox_defconfig b/configs/sandbox_defconfig
index 8e0c4cd..e69f147 100644
--- a/configs/sandbox_defconfig
+++ b/configs/sandbox_defconfig
@@ -38,4 +38,4 @@
 CONFIG_DM_RTC=y
 CONFIG_ERRNO_STR=y
 CONFIG_CMD_UT_TIME=y
-CONFIG_DM_TEST=y
+CONFIG_UT_DM=y