PCI hotplug: add pci_configure_slot()

This patch adds a new pci_configure_slot() function that programs the
PCI bus characteristics for a newly-added device.  This is based on
code in pciehp_pci.c, but should be generic enough to be used by pciehp,
shpchp, and acpiphp.

The hotplug_params struct and the program_hpp_typeX() functions are based
on the ACPI definitions, but they aren't really ACPI-specific, and there's
no alternate implementation, so I don't see the need to abstract them yet.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Reviewed-by: Alex Chiang <achiang@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>