lavfi/af_dynaudnorm: replace round by lrint

lrint is at least as fast, uses a superior rounding mode, and avoids an
implicit cast.
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>

libavfilter/af_dynaudnorm.c

@@ -135,7 +135,7 @@ static int query_formats(AVFilterContext *ctx)
 
 static inline int frame_size(int sample_rate, int frame_len_msec)
 {
-    const int frame_size = round((double)sample_rate * (frame_len_msec / 1000.0));
+    const int frame_size = lrint((double)sample_rate * (frame_len_msec / 1000.0));
     return frame_size + (frame_size % 2);
 }