struct pci_resource * acpiphp_get_io_resource (struct pci_resource ** head, u32 size);
this function sorts the resource list by size and then returns the first node of ``size'' length that is not in the ISA aliasing window. If it finds a node larger than ``size'' it will split it up.
size must be a power of two.
difference from get_resource is handling of ISA aliasing space.