dm: Use dm.h header when driver mode is used

This header includes things that are needed to make driver build. Adjust
existing users to include that always, even if other dm/ includes are
present

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/clk/at91/pmc.c b/drivers/clk/at91/pmc.c
index 72d52c5..29067fa 100644
--- a/drivers/clk/at91/pmc.c
+++ b/drivers/clk/at91/pmc.c
@@ -7,9 +7,8 @@
 
 #include <common.h>
 #include <clk-uclass.h>
-#include <dm/device.h>
+#include <dm.h>
 #include <dm/lists.h>
-#include <dm/root.h>
 #include <dm/util.h>
 #include "pmc.h"