sfx() with channel -2 to stop sound not working
Calling `sfx()` with the [channel] argument set to `-2` should interrupt (stop) a given sound from playing on any channels it's playing on. I noticed that isn't working properly in this cart: [Pico Joust 2600](https://www.lexaloffle.com/bbs/?tid=50964)

In the linked cart, you can notice the effect when you die and respawn. There's a sound that plays for a long time, increasing up in frequency. It's supposed to be interrupted when you start moving again, with a call to `sfx(6,-2)` in the code. Instead, it plays for its full duration.