ASoC: i.MX SSI driver does not yet support master mode

The clocks for the SSI block need handling before this can work.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/sound/soc/imx/imx-ssi.c b/sound/soc/imx/imx-ssi.c
index ccb7ec9..56f46a7 100644
--- a/sound/soc/imx/imx-ssi.c
+++ b/sound/soc/imx/imx-ssi.c
@@ -133,15 +133,11 @@
 
 	/* DAI clock master masks */
 	switch (fmt & SND_SOC_DAIFMT_MASTER_MASK) {
-	case SND_SOC_DAIFMT_CBS_CFS:
-		strcr |= SSI_STCR_TFDIR | SSI_STCR_TXDIR;
+	case SND_SOC_DAIFMT_CBM_CFM:
 		break;
-	case SND_SOC_DAIFMT_CBM_CFS:
-		strcr |= SSI_STCR_TFDIR;
-		break;
-	case SND_SOC_DAIFMT_CBS_CFM:
-		strcr |= SSI_STCR_TXDIR;
-		break;
+	default:
+		/* Master mode not implemented, needs handling of clocks. */
+		return -EINVAL;
 	}
 
 	strcr |= SSI_STCR_TFEN0;