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/st/stm32f746-disco/stm32f746-disco.c b/board/st/stm32f746-disco/stm32f746-disco.c
index dc3a9dc..aeaa311 100644
--- a/board/st/stm32f746-disco/stm32f746-disco.c
+++ b/board/st/stm32f746-disco/stm32f746-disco.c
@@ -12,7 +12,7 @@
 #include <asm/armv7m.h>
 #include <asm/arch/stm32.h>
 #include <asm/arch/gpio.h>
-#include <dm/platdata.h>
+#include <asm/arch/fmc.h>
 #include <dm/platform_data/serial_stm32x7.h>
 #include <asm/arch/stm32_periph.h>
 #include <asm/arch/stm32_defs.h>