ASoC: soc.h: use bit field for playback/capture_only

Current snd_soc_dai_link is already using many bit fields.
Let's use it for playback_only/capture_only too.
We can reduce struct size in certain environment.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

include/sound/soc.h

@@ -1025,13 +1025,13 @@ struct snd_soc_dai_link {
 	const struct snd_soc_ops *ops;
 	const struct snd_soc_compr_ops *compr_ops;
 
-	/* For unidirectional dai links */
-	bool playback_only;
-	bool capture_only;
-
 	/* Mark this pcm with non atomic ops */
 	bool nonatomic;
 
+	/* For unidirectional dai links */
+	unsigned int playback_only:1;
+	unsigned int capture_only:1;
+
 	/* Keep DAI active over suspend */
 	unsigned int ignore_suspend:1;