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/pinctrl/pinctrl-sandbox.c b/drivers/pinctrl/pinctrl-sandbox.c
index ab03d8b..e77b49c 100644
--- a/drivers/pinctrl/pinctrl-sandbox.c
+++ b/drivers/pinctrl/pinctrl-sandbox.c
@@ -7,7 +7,7 @@
 /* #define DEBUG */
 
 #include <common.h>
-#include <dm/device.h>
+#include <dm.h>
 #include <dm/pinctrl.h>
 
 static const char * const sandbox_pins[] = {