ASoC: audio-graph-card2: indicate "Experimental stage" warning only when successed

Because Sound Card needs many drivers to probe, current audio-graph-card2
will indicate "Experimental stage" at top of probe function even though
in case it gets -EPROBE_DEFER, thus it will be indicated many times.

This patch indicates it when probe was succeeded.

[    1.601393] asoc-audio-graph-card2 sound: Audio Graph Card2 is still under Experimental stage
...
[    1.721269] asoc-audio-graph-card2 sound: Audio Graph Card2 is still under Experimental stage
...
[    1.755231] asoc-audio-graph-card2 sound: Audio Graph Card2 is still under Experimental stage
...
[    1.907710] asoc-audio-graph-card2 sound: Audio Graph Card2 is still under Experimental stage
...
[    1.933173] rcar_sound ec500000.sound: probed
[    1.948875] asoc-audio-graph-card2 sound: Audio Graph Card2 is still under Experimental stage
[    1.959558] asoc-audio-graph-card2 sound: ak4613-hifi <-> rsnd-dai.0 mapping ok
[    1.968119] asoc-audio-graph-card2 sound: i2s-hifi <-> rsnd-dai.1 mapping ok
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87o80vgn5a.wl-kuninori.morimoto.gx@renesas.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/generic/audio-graph-card2.c

@@ -1178,8 +1178,6 @@ int audio_graph2_parse_of(struct asoc_simple_priv *priv, struct device *dev,
 	struct link_info *li;
 	int ret;
 
-	dev_warn(dev, "Audio Graph Card2 is still under Experimental stage\n");
-
 	li = devm_kzalloc(dev, sizeof(*li), GFP_KERNEL);
 	if (!li)
 		return -ENOMEM;
@@ -1245,6 +1243,9 @@ int audio_graph2_parse_of(struct asoc_simple_priv *priv, struct device *dev,
 	if (ret < 0)
 		dev_err_probe(dev, ret, "parse error\n");
 
+	if (ret == 0)
+		dev_warn(dev, "Audio Graph Card2 is still under Experimental stage\n");
+
 	return ret;
 }
 EXPORT_SYMBOL_GPL(audio_graph2_parse_of);