soundwire: intel: add trigger support in sdw dai driver

soundwire: intel: add trigger support in sdw dai driver

The existing code does not expose a trigger callback, which is very
much required for streaming.

The SoundWire stream is enabled and disabled in trigger function.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Rander Wang <rander.wang@linux.intel.com>
Acked-by: Sanyog Kale <sanyog.r.kale@intel.com>
Link: https://lore.kernel.org/r/20200215014740.27580-4-pierre-louis.bossart@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>