ASoC: Add initial support for multiple CPU DAIs

ASoC core supports multiple codec DAIs but supports only a CPU DAI.
To support multiple cpu DAIs, add cpu_dai and num_cpu_dai in
snd_soc_dai_link and snd_soc_pcm_runtime structures similar to
support for codec_dai. This is intended as a preparatory patch to
eventually support the unification of the Codec and CPU DAI.

Inline with multiple codec DAI approach, add support to allocate,
init, bind and probe multiple cpu_dai on init if driver specifies
that. Also add support to loop over multiple cpu_dai during
suspend and resume.

This is intended as a preparatory patch to eventually unify the CPU
and Codec DAI into DAI components.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Shreyas NC <shreyas.nc@intel.com>
Link: https://lore.kernel.org/r/20200225133917.21314-2-yung-chuan.liao@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>