x86/PCI/ACPI: Ignore resources consumed by host bridge itself

When parsing resources for PCI host bridge, we should ignore resources
consumed by host bridge itself and only report window resources available
to child PCI busses.

Fixes: 593669c2

 (x86/PCI/ACPI: Use common ACPI resource interfaces ...)
Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>