input.cpp: initialize m_touchpadsEnabled in addInputDevice
m_touchpadsEnabled gets initialized to true in input.h, and the actual status of the device is not evaluated until the toggleTouchpads setting is pressed.
This fixes the issue by removing m_touchpadsEnabled and refactoring the toggling method. OSD is handled by their respective enable/disable Touchpads methods.
(cherry picked from commit e910dcb9)