PCI: improve discovery/configuration messages

This makes PCI resource management messages more consistent and adds a few
new messages to aid debugging.

Whenever we assign resources to a device, update a BAR, or change a
bridge aperture, it's worth noting it.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>