xf86-video-newport update (round 1)

hi!

I've pulled some of my local xf86-video-newport (sgimips indy
graphics) work into an initial diff. It updates some comments, adds
some TODOs while I have been digging into what's required to keep the
graphics pipeline/FIFO happy, and cleans up how the hardware
programming works to match what I did to the console driver earlier in
the year.

The diff is here:
https://people.freebsd.org/~adrian/netbsd/20260508-netbsd-xf86-video-newport-1.diff
.

I have a bunch more stuff to clean up and land before I tackle the
missing XAA support but this seems like a good first step.

Thanks!


-adrian