dm: core: Drop header files from dm/test.h

These header file should not be included in other header files. Remove
them and add to each individual file. Add test/test.h to test/ui.h since
that is a reasonable place.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/dm/osd.c b/test/dm/osd.c
index 5739dfa..8784867 100644
--- a/test/dm/osd.c
+++ b/test/dm/osd.c
@@ -7,10 +7,11 @@
 #include <common.h>
 #include <display_options.h>
 #include <dm.h>
-#include <dm/test.h>
-#include <test/ut.h>
 #include <video_osd.h>
 #include <asm/test.h>
+#include <dm/test.h>
+#include <test/test.h>
+#include <test/ut.h>
 
 #include "../../drivers/video/sandbox_osd.h"