PCI hotplug: acpiphp: use generic pci_configure_slot()

Use the generic pci_configure_slot() rather than the acpiphp-specific
decode_hpp() and program_hpp().

Unlike the previous acpiphp-specific code, pci_configure_slot() programs
PCIe settings when an _HPX method provides them, so acpiphp-managed PCIe
devices can now be configured.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Reviewed-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Acked-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>