[PATCH] Driver core: allow struct device to have a dev_t

This is the first step in moving class_device to being replaced by
struct device.  It allows struct device to export a dev_t and makes it
easy to dynamically create and destroy struct device as long as they are
associated with a specific class.

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