ALSA: pcm: Define snd_pcm_lib_preallocate_*() as returning void

Now all callers no longer check the return value from
snd_pcm_lib_preallocate_pages() and co, let's make them to return
void, so that any new code won't fall into the same pitfall.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index ca20f80..465d7d0 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -1185,12 +1185,12 @@ static inline void snd_pcm_gettime(struct snd_pcm_runtime *runtime,
  *  Memory
  */
 
-int snd_pcm_lib_preallocate_free(struct snd_pcm_substream *substream);
-int snd_pcm_lib_preallocate_free_for_all(struct snd_pcm *pcm);
-int snd_pcm_lib_preallocate_pages(struct snd_pcm_substream *substream,
+void snd_pcm_lib_preallocate_free(struct snd_pcm_substream *substream);
+void snd_pcm_lib_preallocate_free_for_all(struct snd_pcm *pcm);
+void snd_pcm_lib_preallocate_pages(struct snd_pcm_substream *substream,
 				  int type, struct device *data,
 				  size_t size, size_t max);
-int snd_pcm_lib_preallocate_pages_for_all(struct snd_pcm *pcm,
+void snd_pcm_lib_preallocate_pages_for_all(struct snd_pcm *pcm,
 					  int type, void *data,
 					  size_t size, size_t max);
 int snd_pcm_lib_malloc_pages(struct snd_pcm_substream *substream, size_t size);