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/clk-main.c b/drivers/clk/at91/clk-main.c
index 252d076..a234ce8 100644
--- a/drivers/clk/at91/clk-main.c
+++ b/drivers/clk/at91/clk-main.c
@@ -7,7 +7,7 @@
 
 #include <common.h>
 #include <clk-uclass.h>
-#include <dm/device.h>
+#include <dm.h>
 #include <linux/io.h>
 #include <mach/at91_pmc.h>
 #include "pmc.h"