ASoC: Make soc_find_matching_codec() static

The function is only used locally, make it static.

Fixes the following warning from sparse:
	sound/soc/soc-core.c:1644:22: warning: symbol 'soc_find_matching_codec' was not declared. Should it be static?

Fixes: 3ca041ed ("ASoC: dt: Allow Aux Codecs to be specified using DT")
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-By: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Mark Brown <broonie@linaro.org>

sound/soc/soc-core.c

@@ -1543,7 +1543,8 @@ static void soc_unregister_ac97_dai_link(struct snd_soc_codec *codec)
 }
 #endif
 
-struct snd_soc_codec *soc_find_matching_codec(struct snd_soc_card *card, int num)
+static struct snd_soc_codec *soc_find_matching_codec(struct snd_soc_card *card,
+	int num)
 {
 	struct snd_soc_aux_dev *aux_dev = &card->aux_dev[num];
 	struct snd_soc_codec *codec;