Fix Wio Terminal ButtonController (#620)

[pabigot]

Summary

If debounce isn't enabled pinstate always returns zero, so the code treats every event as a down state.

Fixes #620. It seems like the original code should work, but the id() method isn't available because a trait bound is unsatisfied. My rust-fu isn't strong enough yet to figure out what's going on to explain this, but it's something to do with the ei macro in hal/src/thumbv7em/eic/pin.rs.

Checklist

• [ ] CHANGELOG.md for the BSP or HAL updated
• [ ] All new or modified code is well documented, especially public items
• [ ] No new warnings or clippy suggestions have been introduced (see CI or check locally)