ALSA: pcm: Make constraints lists const

They aren't modified by the core so the drivers can declare them const.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index 68372bc..e91e604 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -810,7 +810,7 @@
 int snd_pcm_hw_constraint_list(struct snd_pcm_runtime *runtime, 
 			       unsigned int cond,
 			       snd_pcm_hw_param_t var,
-			       struct snd_pcm_hw_constraint_list *l);
+			       const struct snd_pcm_hw_constraint_list *l);
 int snd_pcm_hw_constraint_ratnums(struct snd_pcm_runtime *runtime, 
 				  unsigned int cond,
 				  snd_pcm_hw_param_t var,