spapr_pci: Drop some dead error handling

spapr_pci: Drop some dead error handling

chassis_from_bus() uses object_property_get_uint() to get property
"chassis_nr" of the bridge device.  Failure would be a programming
error.  Pass &error_abort, and simplify its callers.

Cc: David Gibson <[email protected]>
Cc: [email protected]
Signed-off-by: Markus Armbruster <[email protected]>
Acked-by: David Gibson <[email protected]>
Reviewed-by: Greg Kurz <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Reviewed-by: Paolo Bonzini <[email protected]>
Message-Id: <20200505152926[email protected]>