ASoC: Intel: boards: sof_sdw: add SoundWire mockup codecs for tests

Add support for SoundWire mockup devices. The configurations assume the
same topology as the CML SoundWire devices and can be used to test the
SOF firmware on a development board (RVP, UpExtreme) without any
hardware connected.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20210714032209.11284-5-yung-chuan.liao@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>