ASoC: dapm - Add DAPM stream completion event.

In preparation for Dynamic PCM (AKA DSP) support.

This adds a callback function to be called at the completion of a DAPM stream
event.

This can be used by DSP components to perform calculations based on DAPM graphs
after completion of stream events.

Signed-off-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

include/sound/soc-dapm.h

@@ -524,6 +524,8 @@ struct snd_soc_dapm_context {
 	enum snd_soc_bias_level target_bias_level;
 	struct list_head list;
 
+	int (*stream_event)(struct snd_soc_dapm_context *dapm, int event);
+
 #ifdef CONFIG_DEBUG_FS
 	struct dentry *debugfs_dapm;
 #endif