ASoC: SOF: clarify use of widget complete flag

ASoC: SOF: clarify use of widget complete flag

Currently, the complete flag is used only for the snd_soc_dapm_scheduler
type widgets to indicate that the pipeline has been set up. All other
widgets do not need it. Add a comment to clarify its usage and set the
complete flag to false only for the scheduler widget in
sof_widget_free().

Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20220426171743.171061-11-ranjani.sridharan@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>