ffplay: compact expression in compute_mod()

Prefer "return X ? Y : Z" over "if (x) return Y; else return Z",
reduce line count.
Signed-off-by: Stefano Sabatini <stefano.sabatini-lala@poste.it>

ffplay.c

@@ -771,11 +771,7 @@ static void video_image_display(VideoState *is)
 
 static inline int compute_mod(int a, int b)
 {
-    a = a % b;
-    if (a >= 0)
-        return a;
-    else
-        return a + b;
+    return a < 0 ? a%b + b : a%b;
 }
 
 static void video_audio_display(VideoState *s)