x86/PCI: add host bridge resource release for _CRS path

1. Allocate pci_root_info instead of using stack.  We need to pass around
   info for release function.
2. Add release_pci_root_info
3. Set x86 host bridge release function to make sure root bridge
   related resources get freed during root bus removal.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>