pci_dw.c: Set IO ATU window correctly

[kd]

Summary

Use viewport "2" instead of "0" and change window type from MEM to IO.
Without these changes the MEM ATU window is overwritten with the IO one.
On macchiatobin memory window is mapped 1:1, i.e no address translation is done which is why PCI works fine there.
This issue was discovered on a different board running a similar SoC to macchiatobin.