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:

  pci_scan_one_pbm()
    pci_add_resource_offset(&resources, &pbm->io_space, pbm->io_space.start);
    pci_add_resource_offset(&resources, &pbm->mem_space, pbm->mem_space.start);
    pci_add_resource_offset(&resources, &pbm->mem64_space, pbm->mem_space.start);

so pcibios_resource_to_bus() knows how to do that translation.

No functional change intended.

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