ASoC: max98090: Guard runtime PM callbacks

Otherwise the functions will be defined but unreferenced when runtime PM
is disabled, generating warnings.
Signed-off-by: Mark Brown <broonie@linaro.org>

sound/soc/codecs/max98090.c

@@ -2350,6 +2350,7 @@ static int max98090_i2c_remove(struct i2c_client *client)
 	return 0;
 }
 
+#ifdef CONFIG_PM_RUNTIME
 static int max98090_runtime_resume(struct device *dev)
 {
 	struct max98090_priv *max98090 = dev_get_drvdata(dev);
@@ -2369,6 +2370,7 @@ static int max98090_runtime_suspend(struct device *dev)
 
 	return 0;
 }
+#endif
 
 static const struct dev_pm_ops max98090_pm = {
 	SET_RUNTIME_PM_OPS(max98090_runtime_suspend,