During testing remove/rescan root bus 00, found
[  338.142574] bus: 'pci': really_probe: probing driver ata_piix with device 0000:00:01.1
[  338.146788] ata_piix 0000:00:01.1: device not available (can't reserve [io  0x01f0-0x01f7])
[  338.150565] ata_piix: probe of 0000:00:01.1 failed with error -22

because that fixed resource is not claimed.
For bootint path it is claimed in  from
        arch/x86/pci/i386.c::pcibios_allocate_resources()

Claim those resources, so on the remove/rescan will still use old
resources.

It is some kind honoring FW setting in the registers during hot add.
esp root-bus hot add is through acpi, BIOS has chance to set some registers
before handing over.

[bhelgaas: move weak definition to patch that uses it]
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>