s390/pci: handle stale deconfiguration events

The PCIs event with PEC 0x0303 or 0x0304 are a request to deconfigure
a PCI function, respectively an indication that it was already
deconfigured by the platform. If such an event is queued during boot it
may happen that the platform has already adjusted the configuration flag
of the relevant function in the CLP List PCI Functions result. In this
case we might not have configured the PCI function at all and should
thus ignore the event. Note that no locking is necessary as event
handling only starts after we have fully initialized the zPCI subsystem
and scanned all PCI devices listed in the CLP result.

Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Acked-by: Pierre Morel <pmorel@linux.ibm.com>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>