avcodec/aacdec_fixed: Fix undefined integer overflow in apply_independent_coupling_fixed()

Fixes: signed integer overflow: 1195517 * 2048 cannot be represented in type 'int'
Fixes: 8636/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_AAC_FIXED_fuzzer-4695836326887424

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

libavcodec/aacdec_fixed.c

@@ -436,7 +436,7 @@ static void apply_independent_coupling_fixed(AACContext *ac,
     else {
       for (i = 0; i < len; i++) {
           tmp = (int)(((int64_t)src[i] * c + (int64_t)0x1000000000) >> 37);
-          dest[i] += tmp * (1 << shift);
+          dest[i] += tmp * (1U << shift);
       }
     }
 }