[PATCH] generate hotplug events for cpu online

We already do kobject_hotplug for cpu offline; this adds a kobject_hotplug
call for the online case.  This is being requested by developers of an
application which wants to be notified about both kinds of events.

Signed-off-by: Nathan Lynch <ntl@pobox.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>