Input: gpio_keys_polled - 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 gpio_keys_polled driver to use
the polling mode of standard input devices and removes dependency on
INPUT_POLLDEV.

Note that we still keep polled and non-polled gpio-keys drivers separate,
as they are different enough and mixing them up would make the code pretty
confusing.

Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Marco Felsch <m.felsch@pengutronix.de>
Link: https://lore.kernel.org/r/20191017204217.106453-9-dmitry.torokhov@gmail.com


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