Document why we ignore overflows in pvmp3_st_intensity

Bug: 170373840
Test: poc in bug description
Test: atest Mp3DecoderTest -- --enable-module-dynamic-download=true
Test: atest VtsHalMediaC2V1_0TargetAudioDecTest
Change-Id: I8fa1dcfb2161e2ff4427e06ae2a23e0bb08c3d83
1 file changed