ASoC: max98090: Make struct dev_pm_ops const

Silences the following checkpatch warning:
WARNING: struct dev_pm_ops should normally be const.
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/codecs/max98090.c

@@ -2362,7 +2362,7 @@ static int max98090_runtime_suspend(struct device *dev)
 	return 0;
 }
 
-static struct dev_pm_ops max98090_pm = {
+static const struct dev_pm_ops max98090_pm = {
 	SET_RUNTIME_PM_OPS(max98090_runtime_suspend,
 		max98090_runtime_resume, NULL)
 };