soundwire: intel: enable test modes

This patch adds debugfs support to override the Master and Slave data
modes. The settings only take effect prior to a new stream being
prepared/enabled, or on resume.

The test mode can be set to verify data integrity and detect bus
clashes, but can only be used to test capture paths. In this case the
input generated by a Slave source port is replaced by a fixed or
cyclical patterns.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@linux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20200920193207.31241-3-yung-chuan.liao@linux.intel.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>