avcodec/diracdsp: Fix integer overflow in PUT_SIGNED_RECT_CLAMPED()

Fixes: runtime error: signed integer overflow: 2147483646 + 2048 cannot be represented in type 'int'
Fixes: 4479/clusterfuzz-testcase-minimized-6529894147162112

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

libavcodec/diracdsp.c

@@ -159,10 +159,10 @@ static void put_signed_rect_clamped_ ## PX ## bit_c(uint8_t *_dst, int dst_strid
     int32_t *src = (int32_t *)_src;                                                                     \
     for (y = 0; y < height; y++) {                                                                      \
         for (x = 0; x < width; x+=4) {                                                                  \
-            dst[x  ] = av_clip_uintp2(src[x  ] + (1 << (PX - 1)), PX);                                  \
-            dst[x+1] = av_clip_uintp2(src[x+1] + (1 << (PX - 1)), PX);                                  \
-            dst[x+2] = av_clip_uintp2(src[x+2] + (1 << (PX - 1)), PX);                                  \
-            dst[x+3] = av_clip_uintp2(src[x+3] + (1 << (PX - 1)), PX);                                  \
+            dst[x  ] = av_clip_uintp2(src[x  ] + (1U << (PX - 1)), PX);                                  \
+            dst[x+1] = av_clip_uintp2(src[x+1] + (1U << (PX - 1)), PX);                                  \
+            dst[x+2] = av_clip_uintp2(src[x+2] + (1U << (PX - 1)), PX);                                  \
+            dst[x+3] = av_clip_uintp2(src[x+3] + (1U << (PX - 1)), PX);                                  \
         }                                                                                               \
         dst += dst_stride >> 1;                                                                         \
         src += src_stride >> 2;                                                                         \