Adding software support for enabling the pure gpio capability of the
device - which allows all I/O to be used as GPIO. Previously, I/O
configuration was limited by software to partial GPIO support only.

When working in a pure gpio mode, the device does not require the
certain properties and hence, the following are now made optional:
	- interrupts
	- keypad,num-rows
	- keypad,num-columns
	- linux,keymap

However, note that the above are required to be specified when
configuring the device as a keypad, for which dependencies have been added
such that specifying either one requires the remaining as well.

Also, note that interrupts are made optional, but required when the device
has either been configured in keypad mode or as an interrupt controller.
This has been done since they may not necessarily be used when leveraging
the device purely for GPIO.
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Utsav Agarwal <utsav.agarwal@analog.com>
Link: https://lore.kernel.org/r/20240826-adp5588_gpio_support-v11-3-3e5ac2bd31b7@analog.comSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>