[coreboot] T420 Optimus/NVIDIA GPU support

[Intel Miner]

Hi everyone,

Apologies if this is the wrong place to ask about this, but

I'm eyeing off buying a Lenovo T420 ThinkPad, specifically one with the
NVIDIA GPU, with "Optimus" support

The information I can dig up on the initial support says that the NVIDIA
GPU models are NOT supported by Coreboot

However I see in the hybrid_graphics.c file that there's a listing for the
"T420/T520" (the T520 seemingly /does/ support the NVIDIA GPU?)

I can't seem to find any up-to-date information either way regarding the
GPU status in the T420 however. Any information regarding this would be
appreciated :)

(Alternatively I could just purchase one, build Coreboot and try, of
course!)