[PATCH] Driver Core: add the ability for class_device structures to be nested

This patch allows struct class_device to be nested, so that another
struct class_device can be the parent of a new one, instead of only
having the struct class be the parent.  This will allow us to
(hopefully) fix up the input and video class subsystem mess.

But please people, don't go crazy and start making huge trees of class
devices, you should only need 2 levels deep to get everything to work
(remember to use a class_interface to get notification of a new class
device being added to the system.)

Oh, this also allows us to have the possibility of potentially, someday,
moving /sys/block into /sys/class.  The main hindrance is that pesky
/dev numberspace issue...

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>