utils: fix integer overflow with DURATION_MAX_READ_SIZE

Fixes CID703746
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/utils.c

@@ -2155,7 +2155,7 @@ static void estimate_timings_from_bit_rate(AVFormatContext *ic)
     }
 }
 
-#define DURATION_MAX_READ_SIZE 250000
+#define DURATION_MAX_READ_SIZE 250000LL
 #define DURATION_MAX_RETRY 4
 
 /* only usable for MPEG-PS streams */