Input: adc-joystick - add polled input device support

Add polled input device support to the adc-joystick driver. This is
useful for devices which do not have hardware capable triggers on
their SARADC. Code modified from adc-joystick.c changes made by Maya
Matuszczyk.

Signed-off-by: Maya Matuszczyk <maccraft123mc@gmail.com>
Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Link: https://lore.kernel.org/r/20220816210440.14260-3-macroalpha82@gmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Input: adc-joystick - fix ordering in adc_joystick_probe()

We should register the IIO buffer before we register the input device,
because as soon as the device is registered input handlers may attach to
it, resulting in a call to adc_joystick_open() which makes use of the said
buffer.

Acked-by: Artur Rojek <contact@artur-rojek.eu>
Link: https://lore.kernel.org/r/YskFh4NHnlcryMkk@google.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Input: joystick - add ADC attached joystick driver.

Add a driver for joystick devices connected to ADC controllers
supporting the Industrial I/O subsystem.

Signed-off-by: Artur Rojek <contact@artur-rojek.eu>
Tested-by: Paul Cercueil <paul@crapouillou.net>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20200927123302.31062-2-contact@artur-rojek.eu
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>