Input: adc-keys - switch to using polled mode of input devices

We have added polled mode to the normal input devices with the intent of
retiring input_polled_dev. This converts adc-keys driver to use the
polling mode of standard input devices and removes dependency on
INPUT_POLLDEV.

Acked-by: Marco Felsch <m.felsch@pengutronix.de>
Link: https://lore.kernel.org/r/20191017204217.106453-6-dmitry.torokhov@gmail.com


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