virHostdevReAttachPCIDevices: Separate out function body

virHostdevReAttachPCIDevices: Separate out function body

In near future we will have a list of PCI devices we want to
re-attach to the host (held in virPCIDeviceListPtr) but we don't
have virDomainHostdevDefPtr. That's okay because
virHostdevReAttachPCIDevices() works with virPCIDeviceListPtr
mostly anyway. And in very few places where it needs
virDomainHostdevDefPtr are not interesting for our case.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
ACKed-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Cole Robinson <crobinso@redhat.com>