pcm_volume: "length" is a "size_t", not "int"

src/pcm_volume.c

@@ -138,7 +138,7 @@ pcm_volume_change_32(int32_t *buffer, unsigned num_samples, int volume)
 }
 
 bool
-pcm_volume(void *buffer, int length,
+pcm_volume(void *buffer, size_t length,
 	   enum sample_format format,
 	   int volume)
 {

src/pcm_volume.h

@@ -68,7 +68,7 @@ pcm_volume_dither(void)
  * @return true on success, false if the audio format is not supported
  */
 bool
-pcm_volume(void *buffer, int length,
+pcm_volume(void *buffer, size_t length,
 	   enum sample_format format,
 	   int volume);