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

when step into runtime_suspend, spdif 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_spdif.c

@@ -65,6 +65,7 @@ static int __maybe_unused rk_spdif_runtime_suspend(struct device *dev)
 {
 	struct rk_spdif_dev *spdif = dev_get_drvdata(dev);
 
+	regcache_cache_only(spdif->regmap, true);
 	clk_disable_unprepare(spdif->mclk);
 	clk_disable_unprepare(spdif->hclk);
 
@@ -88,7 +89,16 @@ static int __maybe_unused rk_spdif_runtime_resume(struct device *dev)
 		return ret;
 	}
 
-	return 0;
+	regcache_cache_only(spdif->regmap, false);
+	regcache_mark_dirty(spdif->regmap);
+
+	ret = regcache_sync(spdif->regmap);
+	if (ret) {
+		clk_disable_unprepare(spdif->mclk);
+		clk_disable_unprepare(spdif->hclk);
+	}
+
+	return ret;
 }
 
 static int rk_spdif_hw_params(struct snd_pcm_substream *substream,