ASoC: SOF: OF: Add shutdown callback for SOF OF device

Add shutdown callback function for SOF OF device and call
snd_sof_device_shutdown in sof_of_shutdown callback for DSP
shutdown sequence.

Signed-off-by: YC Hung <yc.hung@mediatek.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://lore.kernel.org/r/20220406194048.289787-2-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>