Currently pci_find_domain() performs two functions - it locates the PCI
root bus above the given bus, then looks up that root bus's domain number.
This patch adds a helper function to perform the first task, finding the
root bus for a given PCI device. This is then used in pci_find_domain().
This changes pci_find_domain()'s signature slightly, taking a PCIDevice
instead of a PCIBus - since all callers passed something of the form
dev->bus, this simplifies things slightly.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
c473d18da1