avcodec/sbrdsp_fixed: Fix integer overflow

Fixes: signed integer overflow: 2147483598 + 64 cannot be represented in type 'int'
Fixes: 4337/clusterfuzz-testcase-minimized-6192658616680448

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

libavcodec/sbrdsp_fixed.c

@@ -133,7 +133,7 @@ static av_always_inline SoftFloat autocorr_calc(int64_t accu)
 
         round = 1U << (nz-1);
         mant = (int)((accu + round) >> nz);
-        mant = (mant + 0x40)>>7;
+        mant = (mant + 0x40LL)>>7;
         mant *= 64;
         expo = nz + 15;
         return av_int2sf(mant, 30 - expo);