ASoC: Intel: mrfld: Fix runtime pm calls in sst_open_pcm_stream

It's already done in open/close.

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>