drivers/edac: fix edac_pci sysfs

This patch fixes sysfs exit code for the EDAC PCI device in a similiar manner
and the previous fixes for EDAC_MC and EDAC_DEVICE.

It removes the old (and incorrect) completion model and uses reference counts
on per instance kobjects and on the edac core module.

This pattern was applied to the edac_mc and edac_device code, but the EDAC PCI
code was missed.  In addition, this fixes a system hang after a low level
driver was unloaded.  (A cleanup function was called twice, which really
screwed things up)

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