Clipping is done as it was preferred in review
See: [FFmpeg-devel] [PATCH 1/5] avcodec/atrac9dec: Check precision_fine/coarse

Fixes: out of array access
Fixes: 18330/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ATRAC9_fuzzer-5641113058148352
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>