avcodec/dirac_dwt: Fix integer overflow in COMPOSE_DD97iH0 / COMPOSE_DD137iL0

Fixes: negation of -2147483648 cannot be represented in type 'int32_t' (aka 'int');
Fixes: 6500/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_DIRAC_fuzzer-4523620274536448

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

libavcodec/dirac_dwt.h

@@ -99,10 +99,10 @@ void ff_spatial_idwt_slice2(DWTContext *d, int y);
     (b1 + (unsigned)((int)(b0 + (unsigned)(b2) + 1) >> 1))
 
 #define COMPOSE_DD97iH0(b0, b1, b2, b3, b4)\
-    (int)(((unsigned)(b2) + ((int)(-b0 + 9U*b1 + 9U*b3 - b4 + 8) >> 4)))
+    (int)(((unsigned)(b2) + ((int)(9U*b1 + 9U*b3 - b4 - b0 +  8) >> 4)))
 
 #define COMPOSE_DD137iL0(b0, b1, b2, b3, b4)\
-    (int)(((unsigned)(b2) - ((int)(-b0 + 9U*b1 + 9U*b3 - b4 + 16) >> 5)))
+    (int)(((unsigned)(b2) - ((int)(9U*b1 + 9U*b3 - b4 - b0 + 16) >> 5)))
 
 #define COMPOSE_HAARiL0(b0, b1)\
     ((int)(b0 - (unsigned)((int)(b1 + 1U) >> 1)))