ASoC: Intel: sst: add runtime power management handling

This patch adds the runtime pm handlers, the driver already has code for
get/put for runtime pm and only these handlers being missing.

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>