sdl_impl: Revert to the "old" method of mapping sticks

Not all controllers have a SDL_GameController binding. This caused controllers not present in the SDL GameController database to have buttons mapped instead of axes.

Furthermore, it was not possible to invert the axes when it could be useful such as emulating a horizontal single joycon or other potential cases. This allows us to invert the axes by reversing the order of mapping (vertical, then horizontal).