ASoC: cleasnup rtd and its ID

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

rtd has own ID, but it is naming "num" for it. The naming is confusable.
This patch rename it to "id".
And many functions request both "rtd" and its "id" as function parameter,
but rtd itself has rtd->id. This patch cleanup it.

And, Qcom driver want to use irregular rtd ID because of its topology,
and thus, soc-core need irregular calculation. I'm not sure why only Qcom
needs such calculation, but this patch also cleanup it.
But I guess we want to cleanup is not soc-core but Qcom side (?)