Add VIR_DOMAIN_HOSTDEV_PCI_BACKEND_XEN. For legacy xen, it will use "pciback" as
stub driver.

Changes parameter from vm def to specific hostdevs info and name info, so that
it could be used more widely, e.g, could be used without full vm def info.

Some virHostdevXXXX methods included the string Hostdev again
as a suffix. Change the latter to Device instead.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Change any method names with Usb, Pci or Scsi to use
USB, PCI and SCSI since they are abbreviations.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Various methods in virnetdev.c and virhostdev.c were missing
const-ness for several char * parameters.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Extract general code from qemuDomainReAttachHostScsiDevices to
virHostdevDomainReAttachHostScsiDevices.

Extract general code from qemuDomainReAttachHostUsbDevices to
virHostdevDomainReAttachHostUsbDevices.

Extract general code from qemuPrepareHostSCSIDevices to
virHostdevPrepareHostSCSIDevices.

Extract general code from qemuPrepareHostUSBDevices to
virHostdevPrepareHostUSBDevices.

Extract general code from qemuUpdateActiveScsiHostdevs to
virHostdevUpdateActiveScsiHostdevs

Extract general code from qemuUpdateActiveUsbHostdevs to
virHostdevUpdateActiveUsbHostdevs.

Extract general code from qemuUpdateActivePciHostdevs to
virHostdevUpdateActivePciHostdevs.

Signed-off-by: NChunyan Liu <cyliu@suse.com>

Only wait for kvm device cleanup if the driver is pci-stub

Extract general code from qemuPrepareHostdevPCIDevices to
virHostdevPrepareHostdevPCIDevices.

For extracting hostdev codes from qemu_hostdev.c to common library, change qemu
specific COLD_BOOT handling to be a flag, and pass it to hostdev functions.

For extracting hostdev codes from qemu_hostdev.c to common library, change qemu
specific cfg->relaxedACS handling to be a flag, and pass it to hostdev
functions.

Same logic of preparing/reattaching hostdevs could be used in attach/detach
hotplug places, so reuse hostdev interfaces to avoid duplicate, also for later
extracting general code to common library.

Update parameters from vm->def to specific name, hostdevs, nhostdevs to keep
consistentcy with PreparePCIDevices and PrepareSCSIDevices. And, at the same
time, make it reusable in later patch.

Specify which driver and which domain in used_by area to avoid conflict among
different drivers.
Signed-off-by: NChunyan Liu <cyliu@suse.com>