Firmware: Adjust trackpad for Switch Controller

[arxanas]

Closes #7. This causes the trackpad to only register if you're tapping it (at least, on my Steam Controller). I determined this by uncommenting the debugging statements on these lines:

https://github.com/greggersaurus/OpenSteamController/blob/325801542fcb762d19a91addd801f0630c825966/Firmware/OpenSteamController/src/trackpad.c#L1046-L1054

Basically, during testing, I observed that the sine wave's amplitude correlates directly with the distance of my finger from the trackpad.

[marxjohnson]

I just tested this out and it's a big improvement, thanks for sharing!

[arxanas]

Builds of:

• Firmware with better touch detection. Note that the D-pad is not bound in this firmware, so the left touchpad doesn't do anything.
• My custom Smash Bros. firmware.

custom-firmwares.zip