Input: st1232 - do not unconditionally configure as wakeup source

Do not unconditionally configure the touchscreen as wakeup source but
rather rely on I2C core to do that when requested (either via
"wakeup-source" device property, or when creating a client with
I2C_CLIENT_WAKE flag).

Tested-by: Matthias Fend <Matthias.Fend@wolfvision.net>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>