to eliminate redundant unused members in Wii Remote extension objects.

Change the displayed controls in the TAS Input window when the
controller's extension (including MotionPlus) is changed.

This previously required restarting Dolphin after the attachment was
changed, as the controls were never updated after the WiiTASInputWindow
was created at Dolphin startup.

SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.

casting a value to a u32 when it's originally an int, and it's exposed as int to users,
could end up in cases where a negative number would result as a positive one.
This doesn't really affect the value range of the attachment enum,
still I think the code was wrong.

Heavily tested.