avcodec/dstdec: Fix integer overflow in samples_per_frame computation

Fixes: Timeout (? -> 2ms)
Fixes: 17616/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_DST_fuzzer-5198057947267072

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegReviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/dstdec.c

@@ -37,7 +37,7 @@
 #define DST_MAX_CHANNELS 6
 #define DST_MAX_ELEMENTS (2 * DST_MAX_CHANNELS)
 
-#define DSD_FS44(sample_rate) (sample_rate * 8 / 44100)
+#define DSD_FS44(sample_rate) (sample_rate * 8LL / 44100)
 
 #define DST_SAMPLES_PER_FRAME(sample_rate) (588 * DSD_FS44(sample_rate))