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/panel.c b/test/dm/panel.c
index 7e4ebd6..410e8f3 100644
--- a/test/dm/panel.c
+++ b/test/dm/panel.c
@@ -14,8 +14,9 @@
 #include <asm/gpio.h>
 #include <asm/test.h>
 #include <dm/test.h>
-#include <test/ut.h>
 #include <power/regulator.h>
+#include <test/test.h>
+#include <test/ut.h>
 
 /* Basic test of the panel uclass */
 static int dm_test_panel(struct unit_test_state *uts)