avutil/common: Fix undefined behavior in av_clip_uintp2_c()

Fixes: negation of -2147483648 cannot be represented in type 'int'; cast to an unsigned type to negate this value to itself
Fixes: 8521/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_DIRAC_fuzzer-5639024952737792

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

libavutil/common.h

@@ -228,7 +228,7 @@ static av_always_inline av_const int av_clip_intp2_c(int a, int p)
  */
 static av_always_inline av_const unsigned av_clip_uintp2_c(int a, int p)
 {
-    if (a & ~((1<<p) - 1)) return -a >> 31 & ((1<<p) - 1);
+    if (a & ~((1<<p) - 1)) return (~a) >> 31 & ((1<<p) - 1);
     else                   return  a;
 }