[media] soc_camera: Constify dev_pm_ops in mt9t031.c

Silences the following warning:
WARNING: struct dev_pm_ops should normally be const

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/i2c/soc_camera/mt9t031.c

@@ -570,7 +570,7 @@ static int mt9t031_runtime_resume(struct device *dev)
 	return 0;
 }
 
-static struct dev_pm_ops mt9t031_dev_pm_ops = {
+static const struct dev_pm_ops mt9t031_dev_pm_ops = {
 	.runtime_suspend	= mt9t031_runtime_suspend,
 	.runtime_resume		= mt9t031_runtime_resume,
 };