ASoC: audio-graph-card2: check also dpcm node for convert-xxx

ASoC: audio-graph-card2: check also dpcm node for convert-xxx

DPCM connection on Card2, its DT looks like below.
Current Card2 is checking (a)/(b) part only for convert-xxx settings.
But it is not useful. This patch enables its settings at (A)/(B) part
too. (A)/(B) settings will be overwritten (a)/(b) settings if it has.

<Image>		      (A)	(a)
	Card2 <--+--> FE <---> CPU
		 |
		 +--> BE <---> Codec
		      (B)	(b)

<DT>
	card2-sound {
		...
		links = <fe, be>; /* (A) (B) */
	};

	dpcm {
		/* FE */
		ports@0 {
			/* (A) */
			fe: port { fe_ep: endpoint { remote-endpoint = <&cpu_ep>; } };
		};
		/* BE */
		ports@1 {
			/* (B) */
			be: port {
				convert-rate = <44100>; /* This patch enables this */
				be_ep: endpoint { remote-endpoint = <&codec_ep>; }
			};
		};
	};

	cpu {
		/* CPU (a) */
		port { cpu_ep: endpoint { remote-endpoint = <&fe_ep>; } };
	};

	codec {
		/* Codec (b) */
		port {
			convert-rate = <48000>; /* (B) settings will be over written here */
			codec_ep: endpoint { remote-endpoint = <&be_ep>; }
		};
	};

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/871qqn8fst.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>