ASoC: SOF: Add .prepare/.complete callbacks

Use SOF defined callbacks (snd_sof_prepare/snd_sof_complete)
in order to update internal SOF system suspend target.

Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Reviewed-by: Paul Olaru <paul.olaru@nxp.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Link: https://lore.kernel.org/r/20200924151518.15841-3-daniel.baluta@oss.nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/sof-of-dev.c

@@ -46,6 +46,8 @@ static struct sof_dev_desc sof_of_imx8mp_desc = {
 #endif
 
 static const struct dev_pm_ops sof_of_pm = {
+	.prepare = snd_sof_prepare,
+	.complete = snd_sof_complete,
 	SET_SYSTEM_SLEEP_PM_OPS(snd_sof_suspend, snd_sof_resume)
 	SET_RUNTIME_PM_OPS(snd_sof_runtime_suspend, snd_sof_runtime_resume,
 			   NULL)