If the intention is to push this to pci directory, this code needs to be made
platform agnostic by splitting into two pieces.
I think you can make this code common by abstracting the IRQ number and
have some generic code like pci-wake.c in pci directory without the of prefix
in this file.
Then, you can have some other OF specific code in the drivers/of directory
that reads the IRQ from OF and calls the common code in PCI directory.