Add ids module parameter which allows specifying initial IDs for the
pci-stub driver.  When built into the kernel, pci-stub is linked
before any real pci drivers and by setting up IDs from initialization
it can prevent built-in drivers from attaching to specific devices.

While at it, make pci_stub_probe() print out about devices it grabbed
to weed out "but my controller isn't being probed" bug reports.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>