feat(build): fix compilation on BSD

[ReenigneArcher]

This PR replaces __u16 with std::uint16_t. The motivation for this PR is I am investigating compiling Sunshine on FreeBSD (LizardByte/Sunshine#4049). FreeBSD does not have linux/types.h. I found that using uint16_t does compile past that undefined type error; however, I am not 100% if this is the proper fix. I have an alternate here (ReenigneArcher@e5253e7) if that would be preferred.

[ABeltramo]

I've added a toggle for the uhid implementation so that you can compile inputtino without including it.
If you set USE_UHID to OFF it will fall back to a more basic uinput implementation (which will lack all the advanced features like motion, gyro, trackpad, ...) that should allow you to compile Sunshine on BSD.