acpi_pci: Preserve CPU locality queries for descendants

[kbowling]

Summary

bus_generic_get_cpus() preserves the original leaf device while
forwarding a request through the bus hierarchy. Consequently,
acpi_pci_get_cpus() may receive a descendant below a PCI function
rather than one of the PCI bus's direct children.

Only apply the SR-IOV PF-locality mapping to direct PCI children.
Preserve the previous ACPI CPU-locality lookup for descendants so their
unrelated bus ivars are not interpreted as PCI device information.

MFC after:      2 weeks