ASoC: Intel: mfld-pcm: don't call trigger ops to DSP for internal streams

For internal stream i.e. BE we have don't need trigger ops as that
would be handled by DAPM for us in subsequent patches

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