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 <[email protected]>
Reviewed-by: Greg Kurz <[email protected]>