ACPI: thinkpad-acpi: always track input device open/close

The open() and close() hooks for the input device are useful even when
hotkey NVRAM polling support is not in use, so it is better to always have
them around.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>