Documentation: SoundWire: clarify TDM mode support

Documentation: SoundWire: clarify TDM mode support

The current description of stream topologies does not explicitly
mention 'mirror' topologies used for audio amplifiers, where all
amplifiers see the same data and generate a different output based on
configuration or dynamic information. Add examples and notes to
explain how channels can be transmitted and mapped.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20200419185117.4233-1-yung-chuan.liao@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>