x11/nvidia-driver fix

[Emiel Kollof]

Right, if you do own an nvidia card, and use the nvidia-driver from
dfports, please test this patch at

http://home.hackerheaven.org/~coolvibe/x11-nvidia-driver.diff

I adapted the driver to the new cdevsw_add/remove stuff, no functionality
changes. Just a few questions though:

- is it no longer necessary to call destroy_dev when you detach?
- is it okay to hardcode minor numbers into cdevsw_add() when the
  device is a ctl device (like /dev/nvidiactl with minor 255)?

Please test this first before committing. It works here, but haven't
tested opengl yet because some other panic crept up. Please report.

Committers, if nobody complains or I don't submit new patches in 
three days, commit it please.

Cheers,
Emiel
-- 
. .. A solemn, unsmiling, sanctimonious old iceberg who looked like he
was waiting for a vacancy in the Trinity.
		-- Mark Twain