ASoC: imx: use more robust checking of available streams

Replace the channels_min check with a check for the relevant substream
being present. Suggested here [1] when mxs implemented the
audio-support.

[1] http://www.spinics.net/lists/arm-kernel/msg133010.html

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/imx/imx-pcm-fiq.c

@@ -243,23 +243,22 @@ static int imx_pcm_fiq_new(struct snd_soc_pcm_runtime *rtd)
 	struct snd_card *card = rtd->card->snd_card;
 	struct snd_soc_dai *dai = rtd->cpu_dai;
 	struct snd_pcm *pcm = rtd->pcm;
+	struct snd_pcm_substream *substream;
 	int ret;
 
 	ret = imx_pcm_new(rtd);
 	if (ret)
 		return ret;
 
-	if (dai->driver->playback.channels_min) {
-		struct snd_pcm_substream *substream =
-			pcm->streams[SNDRV_PCM_STREAM_PLAYBACK].substream;
+	substream = pcm->streams[SNDRV_PCM_STREAM_PLAYBACK].substream;
+	if (substream) {
 		struct snd_dma_buffer *buf = &substream->dma_buffer;
 
 		imx_ssi_fiq_tx_buffer = (unsigned long)buf->area;
 	}
 
-	if (dai->driver->capture.channels_min) {
-		struct snd_pcm_substream *substream =
-			pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream;
+	substream = pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream;
+	if (substream) {
 		struct snd_dma_buffer *buf = &substream->dma_buffer;
 
 		imx_ssi_fiq_rx_buffer = (unsigned long)buf->area;

sound/soc/imx/imx-ssi.c

@@ -399,14 +399,14 @@ int imx_pcm_new(struct snd_soc_pcm_runtime *rtd)
 		card->dev->dma_mask = &imx_pcm_dmamask;
 	if (!card->dev->coherent_dma_mask)
 		card->dev->coherent_dma_mask = DMA_BIT_MASK(32);
-	if (dai->driver->playback.channels_min) {
+	if (pcm->streams[SNDRV_PCM_STREAM_PLAYBACK].substream) {
 		ret = imx_pcm_preallocate_dma_buffer(pcm,
 			SNDRV_PCM_STREAM_PLAYBACK);
 		if (ret)
 			goto out;
 	}
 
-	if (dai->driver->capture.channels_min) {
+	if (pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream) {
 		ret = imx_pcm_preallocate_dma_buffer(pcm,
 			SNDRV_PCM_STREAM_CAPTURE);
 		if (ret)