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>
diff --git a/sound/soc/codecs/max98090.c b/sound/soc/codecs/max98090.c
index fef370e..1cf017f 100755
--- a/sound/soc/codecs/max98090.c
+++ b/sound/soc/codecs/max98090.c
@@ -2362,7 +2362,7 @@
 	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)
 };