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/beckhoff/mx53cx9020/mx53cx9020.c b/board/beckhoff/mx53cx9020/mx53cx9020.c
index c5d55dc..e903bc1 100644
--- a/board/beckhoff/mx53cx9020/mx53cx9020.c
+++ b/board/beckhoff/mx53cx9020/mx53cx9020.c
@@ -9,6 +9,7 @@
  */
 
 #include <common.h>
+#include <dm.h>
 #include <asm/io.h>
 #include <asm/arch/imx-regs.h>
 #include <asm/arch/sys_proto.h>
@@ -26,7 +27,6 @@
 #include <linux/fb.h>
 #include <ipu_pixfmt.h>
 #include <fs.h>
-#include <dm/platdata.h>
 #include <dm/platform_data/serial_mxc.h>
 
 enum LED_GPIOS {