drm/nouveau/kms/gv100-: fix spurious window immediate interlocks

Cursor position updates were accidentally causing us to attempt to interlock
window with window immediate, and without a matching window immediate update,
NVDisplay could hang forever in some circumstances.

Fixes suspend/resume on (at least) Quadro RTX4000 (TU104).

Reported-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>