ASoC: Remove unused snd_soc_machine_config declaration

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/include/sound/soc.h b/include/sound/soc.h
index fa1b99b..077dfe4 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -228,7 +228,6 @@
 struct snd_soc_pcm_runtime;
 struct snd_soc_dai;
 struct snd_soc_codec;
-struct snd_soc_machine_config;
 struct soc_enum;
 struct snd_soc_ac97_ops;
 struct snd_soc_clock_info;