ASoC: mediatek: Assign dummy when codec not specified for a DAI link

MediaTek sound card drivers are checking whether a DAI link is present
and used on a board to assign the correct parameters and this is done
by checking the codec DAI names at probe time.

If no real codec is present, assign the dummy codec to the DAI link
to avoid NULL pointer during string comparison.

Fixes: 4302187 ("ASoC: mediatek: common: add soundcard driver common code")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://msgid.link/r/20240313110147.1267793-5-angelogioacchino.delregno@collabora.com
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/mediatek/common/mtk-soundcard-driver.c

@@ -22,7 +22,11 @@ static int set_card_codec_info(struct snd_soc_card *card,
 
 	codec_node = of_get_child_by_name(sub_node, "codec");
 	if (!codec_node) {
-		dev_dbg(dev, "%s no specified codec\n", dai_link->name);
+		dev_dbg(dev, "%s no specified codec: setting dummy.\n", dai_link->name);
+
+		dai_link->codecs = &snd_soc_dummy_dlc;
+		dai_link->num_codecs = 1;
+		dai_link->dynamic = 1;
 		return 0;
 	}