ASoC: remove unnecessary dai_link->platform

Merge series from Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>:

Current ASoC will ignore already connected component when binding Card.
This will happen mainly "CPU Component" is handled as "Platform Component",
which was needed before.

	static int snd_soc_rtd_add_component(...)
	{
		...
		for_each_rtd_components(rtd, i, comp) {
			/* already connected */
			if (comp == component)
				return 0;
		}
		...
	}

Some drivers are still using CPU or Dummy Component as Platform Component,
but these are no meaning or ignored.
This patch-set remove these.