ACPI/PCI: Reset acpi_root_dev->domain to 0 when pci_ignore_seg is set

Reset acpi_root_dev->domain to 0 when pci_ignore_seg is set to keep
consistence between ACPI PCI root device and PCI host bridge device.

Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>