Input: tm2-touchkey - add support for midas touchkey

The touchkey on midas boards is almost identical.
The only real difference is that it uses the same register for both
keycode and base.

Signed-off-by: Simon Shields <simon@lineageos.org>
Signed-off-by: Paweł Chmiel <pawel.mikolaj.chmiel@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>