D3cold support

Hello. nvidia,
My main issue is current linux driver can’t change device power_state to D3cold.

hardware is 8th gen intel + pascal laptop

nouveau kernel driver can change to D3cold, if doesn’t having process that use drm device.

so I’m happy If nvidia driver supported too.

8th gen Intel+Pascal, a rare combination.

now, prime renderer offload on wayland(xwayland) setup,
when wayland composite renderer hasn’t take dgpu(nvidia),
can unload and load dynamically(while running compositor) .
so, nouveau supports d3cold on my machine.