A few devices have a keyboard/keypad which can be slid under the device,
leaving the device with only touch-based interaction. The corresponding kernel
event is reported as SW_KEYPAD_SLIDE [0]. Implement support in libinput.
Since the position of the switch varies across devices, it cannot always be
certain whether the keypad is usable when the switch is in the set position.
Therefore, do not automatically disable the keyboard.
[0] e68d80b13b/include/linux/linux/input-event-codes.h (L885)Closes: #1069
Part-of: <https://gitlab.freedesktop.org/libinput/libinput/-/merge_requests/1242>
