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/board/armltd/integrator/integrator.c b/board/armltd/integrator/integrator.c
index cbe7061..fabb8b1 100644
--- a/board/armltd/integrator/integrator.c
+++ b/board/armltd/integrator/integrator.c
@@ -18,9 +18,9 @@
  */
 
 #include <common.h>
+#include <dm.h>
 #include <netdev.h>
 #include <asm/io.h>
-#include <dm/platdata.h>
 #include <dm/platform_data/serial_pl01x.h>
 #include "arm-ebi.h"
 #include "integrator-sc.h"