x86/PCI: embed pci_sysdata into pci_root_info on ACPI path

Embed the x86 struct pci_sysdata in the struct pci_root_info so it
will be automatically freed in the remove path.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>