mathematics: Make function prototypes identical to definitions

Doxygen gets confused by this.

libavutil/mathematics.h

@@ -97,7 +97,7 @@ int64_t av_rescale(int64_t a, int64_t b, int64_t c) av_const;
  * @return rescaled value a, or if AV_ROUND_PASS_MINMAX is set and a is
  *         INT64_MIN or INT64_MAX then a is passed through unchanged.
  */
-int64_t av_rescale_rnd(int64_t a, int64_t b, int64_t c, enum AVRounding) av_const;
+int64_t av_rescale_rnd(int64_t a, int64_t b, int64_t c, enum AVRounding rnd) av_const;
 
 /**
  * Rescale a 64-bit integer by 2 rational numbers.
@@ -111,7 +111,7 @@ int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq) av_const;
  *         INT64_MIN or INT64_MAX then a is passed through unchanged.
  */
 int64_t av_rescale_q_rnd(int64_t a, AVRational bq, AVRational cq,
-                         enum AVRounding) av_const;
+                         enum AVRounding rnd) av_const;
 
 /**
  * Compare 2 timestamps each in its own timebases.