ASoC: Provide per widget type callback when executing DAPM sequences

Many modern devices have features such as DC servos which take time to start.
Currently these are handled by per-widget events but this makes it difficult
to paralleise operations on multiple widgets, meaning delays can end up
being needlessly serialised. By providing a callback to drivers when all
widgets of a given type have been handled during a DAPM sequence the core
allows drivers to start operations separately and wait for them to complete
much more simply.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>

include/sound/soc.h

@@ -546,6 +546,9 @@ struct snd_soc_codec_driver {
 	/* codec bias level */
 	int (*set_bias_level)(struct snd_soc_codec *,
 			      enum snd_soc_bias_level level);
+
+	void (*seq_notifier)(struct snd_soc_dapm_context *,
+			     enum snd_soc_dapm_type);
 };
 
 /* SoC platform interface */