ASoC: SOF: add runtime idle callback

Add ability to implement a SOF device level runtime idle callback.

Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20190702132428.13129-3-kai.vehmanen@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/intel/hda.h

@@ -457,6 +457,7 @@ int hda_dsp_suspend(struct snd_sof_dev *sdev, int state);
 int hda_dsp_resume(struct snd_sof_dev *sdev);
 int hda_dsp_runtime_suspend(struct snd_sof_dev *sdev, int state);
 int hda_dsp_runtime_resume(struct snd_sof_dev *sdev);
+int hda_dsp_runtime_idle(struct snd_sof_dev *sdev);
 int hda_dsp_set_hw_params_upon_resume(struct snd_sof_dev *sdev);
 void hda_dsp_dump_skl(struct snd_sof_dev *sdev, u32 flags);
 void hda_dsp_dump(struct snd_sof_dev *sdev, u32 flags);