spapr: Fix failure path for attempting to hot unplug PCI bridges

spapr: Fix failure path for attempting to hot unplug PCI bridges

For various technical reasons we can't currently allow unplug a PCI to PCI
bridge on the pseries machine.  spapr_pci_unplug_request() correctly
generates an error message if that's attempted.

But.. if the given errp is not error_abort or error_fatal, it doesn't
actually stop trying to unplug the bridge anyway.

Fixes: 14e714900f6b "spapr: Allow hot plug/unplug of PCI bridges and devices under PCI bridges"
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <groug@kaod.org>
(cherry picked from commit 7aab5899764887f6b0512cb2e5c11bdc2a5d3644)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>