Fix noise osc

[yupferris]

Seems to be wrong in the chrono trigger song "ruined world". It may be something else, but the wind in that song has a lot of jumps in pitch that don't make sense.

[yupferris]

#28 would probably help track this down

[yupferris]

After testing thoroughly in a debugger and checking the code, I couldn't find any obvious errors. Then, I double-checked against the reference from the OST (recorded from hw), and in fact there's no bug at all. The pitch modulation was only more noticeable because of linear resampling (to be fixed in #1) and lack of a post filter (to be fixed in #23).

So, not an issue after all. The emu is correct in this regard already.