sparc/PCI: Implement pci_resource_to_user() with pcibios_resource_to_bus()
"User" addresses are shown in /sys/devices/pci.../.../resource and
/proc/bus/pci/devices and used as mmap offsets for /proc/bus/pci/BB/DD.F
files. On sparc, these are PCI bus addresses, i.e., raw BAR values.
Previously pci_resource_to_user() computed the user address by
subtracting either pbm->io_space.start or pbm->mem_space.start from the
resource start.
We've already told the PCI core about those offsets here: