avcodec/ttadsp: Fix integer overflows in tta_filter_process_c()

Fixes: signed integer overflow: 822841647 + 1647055738 cannot be represented in type 'int'
Fixes: 39935/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_TTA_fuzzer-4592657142251520

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

libavcodec/ttadsp.c

@@ -47,9 +47,9 @@ static void tta_filter_process_c(int32_t *qmi, int32_t *dx, int32_t *dl,
     *error = *in;
     *in += (round >> shift);
 
-    dl[4] = -dl[5]; dl[5] = -dl[6];
-    dl[6] = *in - dl[7]; dl[7] = *in;
-    dl[5] += dl[6]; dl[4] += dl[5];
+    dl[4] = -(unsigned)dl[5]; dl[5] = -(unsigned)dl[6];
+    dl[6] = *in -(unsigned)dl[7]; dl[7] = *in;
+    dl[5] += (unsigned)dl[6]; dl[4] += (unsigned)dl[5];
 }
 
 av_cold void ff_ttadsp_init(TTADSPContext *c)