ASoC: Fix S/PDIF build

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/sound/soc/codecs/spdif_transciever.h b/sound/soc/codecs/spdif_transciever.h
index 296f2eb..1e10212 100644
--- a/sound/soc/codecs/spdif_transciever.h
+++ b/sound/soc/codecs/spdif_transciever.h
@@ -12,6 +12,7 @@
 #ifndef CODEC_STUBS_H
 #define CODEC_STUBS_H
 
+extern struct snd_soc_codec_device soc_codec_dev_spdif_dit;
 extern struct snd_soc_dai dit_stub_dai;
 
 #endif /* CODEC_STUBS_H */