ASoC: SOF: PM: add state machine to comments

Add Audio DSP state machine with comments. Note that the
'D0<-->runtime D0I3' part is not implemented yet.

Signed-off-by: Keyon Jie <yang.jie@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20191111223343.19986-2-pierre-louis.bossart@linux.intel.com


Signed-off-by: Mark Brown <broonie@kernel.org>