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.