To support definitions of s390 pci attributes in Qemu cmdline, we have
to make current S390PCIBusDevice struct inherit DeviceState and add
three properties for it. Currently we only support definitions of uid
and fid.

'uid' is optionally defined by users, identifies a zpci device and
must be defined with a 16-bit and non-zero unique value.

'fid' ranges from 0x0 to 0xFFFFFFFF. For fid property, we introduce a
new PropertyInfo by the name of s390_pci_fid_propinfo with our special
setter and getter. As 'fid' is optional, introduce 'fid_defined' to
track whether the user specified a fid.

'target' field is to direct qemu to find the corresponding generic PCI
device. It is equal to the 'id' value of one of generic pci devices.
If the user doesn't specify 'id' parameter for a generic pci device,
its 'id' value will be generated automatically and use this value as
'target' to create an associated zpci device.

If the user did not specify 'uid' or 'fid', values are generated
automatically. 'target' is required.

In addition, if a pci device has no associated zpci device, the code
will generate a zpci device automatically for it.
Signed-off-by: NYi Min Zhao <zyimin@linux.vnet.ibm.com>
Reviewed-by: NPierre Morel <pmorel@linux.vnet.ibm.com>
Signed-off-by: NCornelia Huck <cornelia.huck@de.ibm.com>