nvagetbios wasn't able to extract the bios.  From what I gathered after
searching, openfirmware handles vbios differently (ie: no checksums, smaller
vbios, etc).  I found a nv34 openfirmware bios someone else dumped and nvbios
is unable to decode the GPIO section.

However, if the aim is ensuring the device has a backlight, I believe it's
already done.  In nouveau_backlight_init, it first checks to ensure there's a
display on either LVDS or eDP.  Can we not reasonably assume that if the gpu
has a LVDS or eDP panel attached that it also has a backlight?  My init
function is a slightly altered version of the existing nv40_backlight_init
function which doesn't have a backlight check either.