of/pci: Fix pci_address_to_pio() conversion of CPU address to I/O port

41f8bba7f5 ("of/pci: Add pci_register_io_range() and
pci_pio_to_address()") added support for systems with several I/O ranges
described by OF bindings.  It modified pci_address_to_pio() look up the
io_range for a given CPU physical address, but the conversion was wrong.

Fix the conversion of address to I/O port.

[bhelgaas: changelog]
Fixes: 41f8bba7f5 ("of/pci: Add pci_register_io_range() and pci_pio_to_address()")
Signed-off-by: Zhichang Yuan <yuanzhichang@hisilicon.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Liviu Dudau <Liviu.Dudau@arm.com>
CC: stable@vger.kernel.org	# v3.18+

drivers/of/address.c

@@ -765,7 +765,7 @@ unsigned long __weak pci_address_to_pio(phys_addr_t address)
 	spin_lock(&io_range_lock);
 	list_for_each_entry(res, &io_range_list, list) {
 		if (address >= res->start && address < res->start + res->size) {
-			addr = res->start - address + offset;
+			addr = address - res->start + offset;
 			break;
 		}
 		offset += res->size;