Input: wacom - don't expose LED inactive option

The LED also indicates the status of the tablet. Don't turn it off.

Reviewed-by: Eduard Hasenleithner <eduard@hasenleithner.at>
Tested-by: Eduard Hasenleithner <eduard@hasenleithner.at>
Signed-off-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>