avcodec/hevc_cabac: Tighten the limit on k in ff_hevc_cu_qp_delta_abs()

Values larger would fail subsequent tests.

Fixes: signed integer overflow: 5 + 2147483646 cannot be represented in type 'int'
Fixes: 16966/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_HEVC_fuzzer-5695709549953024

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

libavcodec/hevc_cabac.c

@@ -642,11 +642,11 @@ int ff_hevc_cu_qp_delta_abs(HEVCContext *s)
     }
     if (prefix_val >= 5) {
         int k = 0;
-        while (k < CABAC_MAX_BIN && get_cabac_bypass(&s->HEVClc->cc)) {
+        while (k < 7 && get_cabac_bypass(&s->HEVClc->cc)) {
             suffix_val += 1 << k;
             k++;
         }
-        if (k == CABAC_MAX_BIN) {
+        if (k == 7) {
             av_log(s->avctx, AV_LOG_ERROR, "CABAC_MAX_BIN : %d\n", k);
             return AVERROR_INVALIDDATA;
         }