ASoC: fsl_ssi: fix kernel panic in probe function

code can raise a panic when the ssi_private->pdev is null

[...]
	/*
	 * If codec-handle property is missing from SSI node, we assume
	 * that the machine driver uses new binding which does not require
	 * SSI driver to trigger machine driver's probe.
	 */
	if (!of_get_property(np, "codec-handle", NULL))
		goto done;
[...]
	ssi_private->pdev =
		platform_device_register_data(&pdev->dev, name, 0, NULL, 0);
[...]
done:
	if (ssi_private->dai_fmt)
		_fsl_ssi_set_dai_fmt(ssi_private, ssi_private->dai_fmt);

Proposal was to not use ssi_private->pdev->dev here but adding a new parameter
of *dev pointer to this _set_dai_fmt() -- passing pdev->dev in probe() and
cpu_dai->dev in fsl_ssi_set_dai_fmt().
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Reported-by: Jean-Michel Hautbois <jean-michel.hautbois@vodalys.com>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/fsl/fsl_ssi.c

@@ -748,8 +748,9 @@ static int fsl_ssi_hw_free(struct snd_pcm_substream *substream,
 	return 0;
 }
 
-static int _fsl_ssi_set_dai_fmt(struct fsl_ssi_private *ssi_private,
-		unsigned int fmt)
+static int _fsl_ssi_set_dai_fmt(struct device *dev,
+				struct fsl_ssi_private *ssi_private,
+				unsigned int fmt)
 {
 	struct regmap *regs = ssi_private->regs;
 	u32 strcr = 0, stcr, srcr, scr, mask;
@@ -758,7 +759,7 @@ static int _fsl_ssi_set_dai_fmt(struct fsl_ssi_private *ssi_private,
 	ssi_private->dai_fmt = fmt;
 
 	if (fsl_ssi_is_i2s_master(ssi_private) && IS_ERR(ssi_private->baudclk)) {
-		dev_err(&ssi_private->pdev->dev, "baudclk is missing which is necessary for master mode\n");
+		dev_err(dev, "baudclk is missing which is necessary for master mode\n");
 		return -EINVAL;
 	}
 
@@ -913,7 +914,7 @@ static int fsl_ssi_set_dai_fmt(struct snd_soc_dai *cpu_dai, unsigned int fmt)
 {
 	struct fsl_ssi_private *ssi_private = snd_soc_dai_get_drvdata(cpu_dai);
 
-	return _fsl_ssi_set_dai_fmt(ssi_private, fmt);
+	return _fsl_ssi_set_dai_fmt(cpu_dai->dev, ssi_private, fmt);
 }
 
 /**
@@ -1387,7 +1388,8 @@ static int fsl_ssi_probe(struct platform_device *pdev)
 
 done:
 	if (ssi_private->dai_fmt)
-		_fsl_ssi_set_dai_fmt(ssi_private, ssi_private->dai_fmt);
+		_fsl_ssi_set_dai_fmt(&pdev->dev, ssi_private,
+				     ssi_private->dai_fmt);
 
 	return 0;