ASoC: SOF: topology: add cpu_dai_name for DAIs

Add the cpu_dai_name member to snd_sof_dai and save the
cpu_dai_name while setting the DAI config.

The internal SOF representation will have to change at a later point
as well when we have multiple CPU dais.

Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>