x86/PCI: read Broadcom CNB20LE host bridge info before PCI scan

We currently read the CNB20LE aperture information in a PCI quirk,
which happens after we've already created the root bus.  This patch
changes it to read the apertures earlier so we can create the root
bus with the correct resources.

I believe the CNB20LE lives at "pci 0000:00:00" based on
https://lkml.org/lkml/2010/8/13/220

CC: Ira W. Snyder <iws@ovro.caltech.edu>
CC: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>