ASoC: SOF: Add system_suspend_target field to struct snd_sof_dev

ASoC: SOF: Add system_suspend_target field to struct snd_sof_dev

Add the system_suspend_target field to struct snd_sof_dev
to track the intended system suspend power target. This will
be used as one of the criteria for determining the
final DSP power state.

Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200129220726.31792-4-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>