driver core: fix docbook for device_private.device

This field refers to the public device struct, not to classes.
Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/base.h

@@ -63,7 +63,7 @@ struct driver_private {
  *	binding of drivers which were unable to get all the resources needed by
  *	the device; typically because it depends on another driver getting
  *	probed first.
- * @device - pointer back to the struct class that this structure is
+ * @device - pointer back to the struct device that this structure is
  * associated with.
  *
  * Nothing outside of the driver core should ever touch these fields.