drm/nv50-: trigger update after all connectors disabled

We were sending the necessary state changes to unset the mode, but
never actually hit the big GO button unless another modeset happens
afterwards.
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nv50_display.c

@@ -1208,6 +1208,7 @@ static void
 nv50_crtc_disable(struct drm_crtc *crtc)
 {
 	struct nv50_head *head = nv50_head(crtc);
+	evo_sync(crtc->dev);
 	if (head->image)
 		nouveau_bo_unpin(head->image);
 	nouveau_bo_ref(NULL, &head->image);