avcodec/hevc_ps: Check log2_sao_offset_scale_*

Fixes: 4868/clusterfuzz-testcase-minimized-6236542906400768
Fixes: runtime error: shift exponent 126 is too large for 32-bit type 'int'

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg


Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>