PCI: Configure *all* devices, not just hot-added ones

There's not really a good way to determine whether firmware has already
configured a device with _HPP/_HPX settings.  On legacy systems, the BIOS
has probably configured everything, but on UEFI systems it is not required
to do so.

Per the PCI Firmware Specification, rev 3.1, sec 3.5, if PCI_COMMAND_IO or
PCI_COMMAND_MEMORY is set, we can assume firmware has set the corresponding
BARs and maybe we can assume it has configured the rest of the device.  And
if a bridge has PCI_COMMAND_PARITY or PCI_COMMAND_SERR set, we can assume
firmware has configured the bridge.  But we can't tell much about devices
without BARs.

I think it should be safe to apply _HPP and _HPX settings anyway, even if
firmware has already configured the device, so configure everything we
find.

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