driver core: create a private portion of struct device

This is to be used to move things out of struct device that no code
outside of the driver core should ever touch.

Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

include/linux/device.h

@@ -28,6 +28,7 @@
 #define BUS_ID_SIZE		20
 
 struct device;
+struct device_private;
 struct device_driver;
 struct driver_private;
 struct class;
@@ -371,6 +372,8 @@ struct device {
 	struct klist_node	knode_bus;
 	struct device		*parent;
 
+	struct device_private	*p;
+
 	struct kobject kobj;
 	char	bus_id[BUS_ID_SIZE];	/* position on parent bus */
 	unsigned		uevent_suppress:1;