ASoC: simple-card: Don't create separate link when platform is present

In normal sound case all DAIs are detected as CPU-Codec.
simple_dai_link_of supports the presence of a platform but it counts
it as a CPU DAI resulting in the creation of an extra link.

Adding a platform property to a link description like:

simple-audio-card,dai-link {
	cpu {
		sound-dai = <&sai1>;
	};
	plat {
		sound-dai = <&dsp>;
	};
	codec {
		sound-dai = <&wm8960>;
	}

will result in the creation of two links:
	* sai1 <-> wm8960
	* dsp  <-> wm8960

which is obviously not what we want. We just want one single link
with:
	* sai1 <-> wm8960 (and platform set to dsp).

Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/20191209135353.17427-1-daniel.baluta@nxp.com


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