At the moment the touch keys have key codes assigned from the device
tree. In some cases, users might want to change the key code from
userspace. There is existing functionality for this in the input core
using the EVIOCSKEYCODE ioctl, which is integrated for example into udev.

Make it possible to use this functionality for tm2-touchkey by simply
making the input core aware of the array that holds the keycodes.
Similar code also exists in mcs_touchkey and mpr121_touchkey.
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20211013112305.41574-2-stephan@gerhold.netSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>