ASoC: SOF: Intel: mtl: define and set power_down_dsp op

ASoC: SOF: Intel: mtl: define and set power_down_dsp op

For MTL platform, dsp cores need to go power down first then dsp subsystem
also need to set power down.

Signed-off-by: Fred Oh <fred.oh@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://lore.kernel.org/r/20220922213644.666315-4-ranjani.sridharan@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>