ASoC: dmaengine-pcm: Make requesting the DMA channel at PCM open optional

Refactor the dmaengine PCM library to allow the DMA channel to be requested
before opening a PCM substream. snd_dmaengine_pcm_open() now expects a DMA
channel instead of a filter function and filter parameter as its parameters.
snd_dmaengine_pcm_close() is updated to not release the DMA channel. This allows
a dmaengine based PCM driver to request its channels before the substream is
opened.

The patch also introduces two new functions, snd_dmaengine_pcm_open_request_chan()
and snd_dmaengine_pcm_close_release_chan(), which have the same signature and
behaviour of the old snd_dmaengine_pcm_{open,close}() and internally use the new
variants of these functions. All users of snd_dmaengine_pcm_{open,close}() are
updated to use snd_dmaengine_pcm_open_request_chan() and
snd_dmaengine_pcm_close_release_chan().

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Tested-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/mxs/mxs-pcm.c

@@ -87,7 +87,7 @@ static int snd_mxs_open(struct snd_pcm_substream *substream)
 
 	snd_soc_set_runtime_hwparams(substream, &snd_mxs_hardware);
 
-	return snd_dmaengine_pcm_open(substream, filter,
+	return snd_dmaengine_pcm_open_request_chan(substream, filter,
 		snd_soc_dai_get_dma_data(rtd->cpu_dai, substream));
 }
 
@@ -104,7 +104,7 @@ static int snd_mxs_pcm_mmap(struct snd_pcm_substream *substream,
 
 static struct snd_pcm_ops mxs_pcm_ops = {
 	.open		= snd_mxs_open,
-	.close		= snd_dmaengine_pcm_close,
+	.close		= snd_dmaengine_pcm_close_release_chan,
 	.ioctl		= snd_pcm_lib_ioctl,
 	.hw_params	= snd_mxs_pcm_hw_params,
 	.trigger	= snd_dmaengine_pcm_trigger,