s390/pci: Highlight failure to enable PCI function

s390/pci: Highlight failure to enable PCI function

Emit an error log when a PCI function cannot be enabled for use, despite
being reported as configured to the system.

This brings to attention situations where functions might go missing
without notice. Going unnoticed is less likely when functions are added
to the system through hotplug, but will produce the same error log.

Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: Gerd Bayer <gbayer@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>