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>
diff --git a/drivers/core/simple-bus.c b/drivers/core/simple-bus.c
index 7dbcbec..b0c2c20 100644
--- a/drivers/core/simple-bus.c
+++ b/drivers/core/simple-bus.c
@@ -5,12 +5,7 @@
 
 #include <common.h>
 #include <dm.h>
-
-struct simple_bus_plat {
-	u32 base;
-	u32 size;
-	u32 target;
-};
+#include <dm/simple_bus.h>
 
 fdt_addr_t simple_bus_translate(struct udevice *dev, fdt_addr_t addr)
 {