ASoC: audio-graph-card2: add Multi CPU/Codec support

This patch adds Multi CPU/Codec support to audio-graph-card2.
Multi CPU/Codec will have connection part (= X) and CPU/Codec list part (= Y).
links indicates connection part of CPU side (= A).

		    +-+   (A)	     +-+
	 CPU1 --(Y) | | <-(X)--(X)-> | | (Y)-- Codec1
	 CPU2 --(Y) | |		     | | (Y)-- Codec2
		    +-+		     +-+

	sound {
		compatible = "audio-graph-card2";

(A)		links = <&mcpu>;

		multi {
			ports@0 {
(X) (A)			mcpu:	port@0 { mcpu0_ep: endpoint { remote-endpoint = <&mcodec0_ep>; }; };
(Y)				port@1 { mcpu1_ep: endpoint { remote-endpoint = <&cpu1_ep>; }; };
(Y)				port@1 { mcpu2_ep: endpoint { remote-endpoint = <&cpu2_ep>; }; };
			};
			ports@1 {
(X)				port@0 { mcodec0_ep: endpoint { remote-endpoint = <&mcpu0_ep>; }; };
(Y)				port@0 { mcodec1_ep: endpoint { remote-endpoint = <&codec1_ep>; }; };
(Y)				port@1 { mcodec2_ep: endpoint { remote-endpoint = <&codec2_ep>; }; };
			};
		};
	};

	CPU {
		ports {
			bitclock-master;
			frame-master;
			port@0 { cpu1_ep: endpoint { remote-endpoint = <&mcpu1_ep>; }; };
			port@1 { cpu2_ep: endpoint { remote-endpoint = <&mcpu2_ep>; }; };
		};
	};

	Codec {
		ports {
			port@0 { codec1_ep: endpoint { remote-endpoint = <&mcodec1_ep>; }; };
			port@1 { codec2_ep: endpoint { remote-endpoint = <&mcodec2_ep>; }; };
		};
	};

Link: https://lore.kernel.org/r/87k0xszlep.wl-kuninori.morimoto.gx@renesas.com
Link: https://lore.kernel.org/r/20210804171748.GC26252@sirena.org.uk


Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/871r4qn8pk.wl-kuninori.morimoto.gx@renesas.com


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