ASoC: rsnd: add multi Component support

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

These are part of "ASoC: add multi Component support" patch-set.
The patch-set supports below case as "2 Cards".

	+-- basic board --------+
	|+--------+             |
	|| CPU ch0| <--> CodecA |
	||     ch1| <-+         |
	|+--------+   |         |
	+-------------|---------+
	+-- expansion board ----+
	|             |         |
	|             +-> CodecB|
	+-----------------------+

Renesas sound driver and its Doc part were held for observation.
Rob mentioned that "definitions" vs "$defs". But I got error on "$defs",
no error on "definitions". I believe this change is not mandatory.

He also mentioned that "reg" is missing, but I also believe that "reg"
is automatically handled somehow/somewhere (I'm not sure detail, but other
reviewer indicated it before).

He also mentioned that "ports" and "port", but added new "ports" needs
special handling. Using "ports" vs "port" are different, not
compatible on this driver. This means we need both on Doc.

Thus, there is no update for these.