ASoC: fsl: fsl_spdif: signedness bug in fsl_spdif_startup()

We need "i" to be signed or it leads to a forever loop in the error
handling.

Fixes: fa3be920 ('ASoC: fsl: fsl_spdif: Check for clk_prepare_enable() error')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/fsl/fsl_spdif.c

@@ -454,7 +454,8 @@ static int fsl_spdif_startup(struct snd_pcm_substream *substream,
 	struct fsl_spdif_priv *spdif_priv = snd_soc_dai_get_drvdata(rtd->cpu_dai);
 	struct platform_device *pdev = spdif_priv->pdev;
 	struct regmap *regmap = spdif_priv->regmap;
-	u32 scr, mask, i;
+	u32 scr, mask;
+	int i;
 	int ret;
 
 	/* Reset module and interrupts only for first initialization */