Hi Nils,
thanks for your patch. I'm sure it works, but there is a small catch: AFAIK the GX2 can use multiple companion chips (CS5530 and CS5536). That means your patch could lead to false positives on some boards. Does the CS5536 appear in lspci on your board? If yes, can you use the CS5536 host bridge PCI ID instead?
Regards, Carl-Daniel