x86/PCI: split out pci_mmconfig_alloc() for code reuse

Split out pci_mmconfig_alloc() for code reuse, which will be used
when supporting PCI root bridge hotplug.

Reviewed-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Jiang Liu <liuj97@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
1 file changed