Revert "PCI: allocate bus resources from the top down"

This reverts commit b126b470.

We're going back to the old behavior of allocating from bus resources
in _CRS order.

Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>