ASoC: soc-pcm: indicate error message at soc_pcm_prepare()

Indicating error message when failed case is very useful for debuging.
In many case, its style is like below.

	int function(...)
	{
		...
		return ret;
	}

	int caller(...)
	{
		...
		ret = function(...);
		if (ret < 0)
			dev_err(...)
		...
	}

This is not so bad, but in this style *each caller* needs to indicate
duplicate same error message, and some caller is forgetting to do it.
And caller can't indicate detail function() error information.

If function() indicates error message, we can get same and
detail information without forgot.

	int function(...)
	{
		...
		if (ret < 0)
			dev_err(...)

		return ret;
	}

	int caller(...)
	{
		...
		ret = function(...);
		...
	}

This patch follow above style at soc_pcm_prepare().

By this patch, dpcm_fe/be_dai_prepare(...)
temporary lacks FE/BE error info, but it will reborn soon.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87o8flutbn.wl-kuninori.morimoto.gx@renesas.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-pcm.c

@@ -852,6 +852,10 @@ static int soc_pcm_prepare(struct snd_pcm_substream *substream)
 
 out:
 	mutex_unlock(&rtd->card->pcm_mutex);
+
+	if (ret < 0)
+		dev_err(rtd->dev, "ASoC: %s() failed (%d)\n", __func__, ret);
+
 	return ret;
 }
 
@@ -2234,11 +2238,8 @@ int dpcm_be_dai_prepare(struct snd_soc_pcm_runtime *fe, int stream)
 			be->dai_link->name);
 
 		ret = soc_pcm_prepare(be_substream);
-		if (ret < 0) {
-			dev_err(be->dev, "ASoC: backend prepare failed %d\n",
-				ret);
+		if (ret < 0)
 			break;
-		}
 
 		be->dpcm[stream].state = SND_SOC_DPCM_STATE_PREPARE;
 	}
@@ -2270,11 +2271,8 @@ static int dpcm_fe_dai_prepare(struct snd_pcm_substream *substream)
 
 	/* call prepare on the frontend */
 	ret = soc_pcm_prepare(substream);
-	if (ret < 0) {
-		dev_err(fe->dev,"ASoC: prepare FE %s failed\n",
-			fe->dai_link->name);
+	if (ret < 0)
 		goto out;
-	}
 
 	fe->dpcm[stream].state = SND_SOC_DPCM_STATE_PREPARE;