ASoC: hdmi-codec: return -ENOTSUPP for digital_mute

snd_soc_dai_digital_mute() will return -ENOTSUPP if driver doesn't
support mute.
In hdmi-codec case, hdmi_codec_digital_mute() will be used for it,
and each driver has .digital_mute() callback.
hdmi_codec_digital_mute() want to return -ENOTSUPP to follow it.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87fta1xxjc.wl-kuninori.morimoto.gx@renesas.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/hdmi-codec.c

@@ -566,7 +566,7 @@ static int hdmi_codec_digital_mute(struct snd_soc_dai *dai, int mute)
 		return hcp->hcd.ops->digital_mute(dai->dev->parent,
 						  hcp->hcd.data, mute);
 
-	return 0;
+	return -ENOTSUPP;
 }
 
 static const struct snd_soc_dai_ops hdmi_codec_i2s_dai_ops = {