ASoC: Intel: add support for platform suspend

This adds support for platform suspend and resume. We ensure all pcms are
suspended by invoking snd_soc_suspend() and then stop the DSP

Signed-off-by: Subhransu S. Prusty <subhransu.s.prusty@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>