avcodec/alac: Check lpc_quant

avcodec/alac: Check lpc_quant

lpc_quant of 0 produces undefined behavior, thus disallow this.
If valid samples use this then such a sample would be quite
usefull to confirm the correct&lossles handling of this.

Fixes: libavcodec/alac.c:218:25: runtime error: shift exponent -1 is negative
Fixes: 15273/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALAC_fuzzer-5656388535058432
Fixes: 15276/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALAC_fuzzer-5761238417539072
Fixes: 15315/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALAC_fuzzer-5767260766994432
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>