drm/tegra: vic: Use autosuspend

When going idle, it's not unlikely that more work will follow.
As such, use autosuspend with a 500ms suspend delay.

Signed-off-by: Mikko Perttunen <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>

drivers/gpu/drm/tegra/vic.c

···
 		if (err < 0)
 			goto unregister_client;
 	}
+	pm_runtime_set_autosuspend_delay(&pdev->dev, 500);
+	pm_runtime_use_autosuspend(&pdev->dev);
 
 	return 0;