ASoC: rockchip: i2s: restore register during runtime_suspend/resume cycle

when step into runtime_suspend, i2s pd will be disabled and loss state.
so need to restore register when runtime_resume.
Signed-off-by: Sugar Zhang <sugar.zhang@rock-chips.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/rockchip/rockchip_i2s.c

@@ -57,6 +57,7 @@ static int i2s_runtime_suspend(struct device *dev)
 {
 	struct rk_i2s_dev *i2s = dev_get_drvdata(dev);
 
+	regcache_cache_only(i2s->regmap, true);
 	clk_disable_unprepare(i2s->mclk);
 
 	return 0;
@@ -73,7 +74,14 @@ static int i2s_runtime_resume(struct device *dev)
 		return ret;
 	}
 
-	return 0;
+	regcache_cache_only(i2s->regmap, false);
+	regcache_mark_dirty(i2s->regmap);
+
+	ret = regcache_sync(i2s->regmap);
+	if (ret)
+		clk_disable_unprepare(i2s->mclk);
+
+	return ret;
 }
 
 static inline struct rk_i2s_dev *to_info(struct snd_soc_dai *dai)