graphics: Support GX2 card+acceleration

The GX2 chip inside the wiiu is a mostly standard Radeon R700-series card, which should be supported by the kernel's radeon driver. However, that driver does everything via the PCI interface, while our card is not on a PCI bus.

Since upstream is unlikely to accept a new driver for a Radeon card, and because a framebuffer really isn't showing the console's abilities off, we need to find a solution to this - be it patching the existing radeon driver or spoofing a PCI bus.