Input: zinitix - add touchkey support

Zinitix touch controllers can use some of the sense lines for virtual
keys (like those found on many phones). Add support for those keys.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Nikita Travkin <nikita@trvn.ru>
Link: https://lore.kernel.org/r/20240717-zinitix-tkey-v5-2-52ea4cd4bd50@trvn.ru


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>