s390/pci: extract software counters from fmb

The software counters are not a part of the function measurement
block. Also we do not check for zdev->fmb != NULL when using these
counters (function measurement can be toggled at runtime). Just move
the software counters to struct zpci_dev.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>