dm: core: Move priv/plat structs for simple_bus to headers

With the new of-platdata, these need to be available to dt_platdata.c
so must be in header files. Move them.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/dm/simple_bus.h

@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright 2020 Google LLC
+ */
+
+#ifndef __DM_SIMPLE_BUS_H
+#define __DM_SIMPLE_BUS_H
+
+struct simple_bus_plat {
+	u32 base;
+	u32 size;
+	u32 target;
+};
+
+#endif