nouveau: console stops updating

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

I tried a NetBSD 10 snapshot with a GTX 970 today.

Sysinst ran fine -- in high resolution! -- but when I booted NetBSD
after the installation, I get the screen update stop as reported in PR
57168 and PR 53126.

So I wonder if why it worked for sysinst, and how I could force my
BIOS to do the same for the installed NetBSD. Any ideas/hints?
 Thomas