gpio: adp5585: support gpi events

gpio: adp5585: support gpi events

Add support for adding GPIs to the event FIFO. This is done by adding
irq_chip support. Like this, one can use the input gpio_keys driver as a
"frontend" device and input handler.

As part of this change, we now implement .request() and .free() as we can't
blindly consume all available pins as GPIOs (example: some pins can be
used for forming a keymap matrix).

Also note that the number of pins can now be obtained from the parent,
top level device. Hence the 'max_gpio' variable can be removed.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20250701-dev-adp5589-fw-v7-15-b1fcfe9e9826@analog.com
Signed-off-by: Lee Jones <lee@kernel.org>