Add zpci_is_vf() helper based on the /sys/bus/pci/devices/<dev>/vfn
attribute which is non-zero for VFs unlike the common code VF number
which starts at 0.
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>