ASoC: rsnd: tidyup rsnd_io_to_runtime() macro

Avoid NULL pointer access
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sh/rcar/rsnd.h

@@ -303,7 +303,8 @@ struct rsnd_dai *rsnd_dai_get(struct rsnd_priv *priv, int id);
 int rsnd_dai_is_play(struct rsnd_dai *rdai, struct rsnd_dai_stream *io);
 int rsnd_dai_id(struct rsnd_priv *priv, struct rsnd_dai *rdai);
 #define rsnd_dai_get_platform_info(rdai) ((rdai)->info)
-#define rsnd_io_to_runtime(io) ((io)->substream->runtime)
+#define rsnd_io_to_runtime(io) ((io)->substream ? \
+				(io)->substream->runtime : NULL)
 
 void rsnd_dai_pointer_update(struct rsnd_dai_stream *io, int cnt);
 int rsnd_dai_pointer_offset(struct rsnd_dai_stream *io, int additional);