audiodsp: fix vector_clipf documentation

The x86 version processes 16 floats per iteration, so len must be a
multiple of 16.

libavcodec/audiodsp.h

@@ -45,7 +45,7 @@ typedef struct AudioDSPContext {
      */
     void (*vector_clip_int32)(int32_t *dst, const int32_t *src, int32_t min,
                               int32_t max, unsigned int len);
-    /* assume len is a multiple of 8, and arrays are 16-byte aligned */
+    /* assume len is a multiple of 16, and arrays are 16-byte aligned */
     void (*vector_clipf)(float *dst /* align 16 */,
                          const float *src /* align 16 */,
                          float min, float max, int len /* align 16 */);