qbus_set_hotplug_handler() is a simple wrapper around
object_property_set_link().

object_property_set_link() fails when the property doesn't exist, is
not settable, or its .check() method fails.  These are all programming
errors here, so passing &error_abort to qbus_set_hotplug_handler() is
appropriate.

Most of its callers do.  Exceptions:

* pcie_cap_slot_init(), shpc_init(), spapr_phb_realize() pass NULL,
  i.e. they ignore errors.

* spapr_machine_init() passes &error_fatal.

* s390_pcihost_realize(), virtio_serial_device_realize(),
  s390_pcihost_plug() pass the error to their callers.  The latter two
  keep going after the error, which looks wrong.

Drop the @errp parameter, and instead pass &error_abort to
object_property_set_link().

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Daniel P. Berrangé" <berrange@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20200630090351.1247703-15-armbru@redhat.com>