ACPI: thinkpad-acpi: export EV_SW SW_RADIO events

The expected user case for the radio slider switch on a ThinkPad includes
interfacing to applications, so that the user gets an offer to find and
associate with a wireless network when the switch is changed from disabled
to enabled (ThinkVantage suite).

Export the information about the switch state, and switch change events as
an EV_SW SW_RADIO event over the input layer.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Ivo van Doorn <ivdoorn@gmail.com>
Cc: Richard Hughes <hughsient@gmail.com>
Signed-off-by: Len Brown <len.brown@intel.com>