Input: imagis - add touch key support

IST3032C (and possibly some other models) has touch keys. Add support
for them to the imagis driver.

Signed-off-by: Duje Mihanović <duje.mihanovic@skole.hr>
Link: https://lore.kernel.org/r/20240306-b4-imagis-keys-v3-3-2c429afa8420@skole.hr
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>