[coreboot] 8GB graphics cards work on coreboot - in case anyone is wondering

[Taiidan at gmx.com]

I was worried that it wouldn't work for some reason like due to lack of
64bit MMIO in coreboot but I just installed an AMD Raden RX580 8GB on my
KGPE-D16 and it works great.

I am playing the latest games on max settings in a VM with a GPU
bottleneck at 1080p with my single 6328 CPU...it is nice to finally have
good smooth gameplay with high fps.