drivers/edac: fix edac_mc sysfs completion code

This patch refactors the 'releasing' of kobjects for the edac_mc type of
device.  The correct pattern of kobject release is followed.

As internal kobjs are allocated they bump a ref count on the top level kobj.
It in turn has a module ref count on the edac_core module.  When internal
kobjects are released, they dec the ref count on the top level kobj.  When the
top level kobj reaches zero, it decrements the ref count on the edac_core
object, allow it to be unloaded, as all resources have all now been released.

Cc: Alan Cox alan@lxorguk.ukuu.org.uk
Signed-off-by: Doug Thompson <dougthompson@xmission.com>
Acked-by: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>