Input: adc-joystick - move axes data into the main structure

There is no need to allocate axes information separately from the main
joystick structure so let's fold the allocation and also drop members
(such as range, flat and fuzz) that are only used during initialization
of the device.

Acked-by: Artur Rojek <contact@artur-rojek.eu>
Link: https://lore.kernel.org/r/ZmkrgTlxNwm_oHxv@google.com


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