ASoC: soc-utils: add const to dummy_codec

Let's align dummy_platform and dummy_codec
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-utils.c

@@ -288,7 +288,7 @@ static const struct snd_soc_platform_driver dummy_platform = {
 	.ops = &dummy_dma_ops,
 };
 
-static struct snd_soc_codec_driver dummy_codec;
+static const struct snd_soc_codec_driver dummy_codec;
 
 #define STUB_RATES	SNDRV_PCM_RATE_8000_192000
 #define STUB_FORMATS	(SNDRV_PCM_FMTBIT_S8 | \