mfd: adp5585: Add support for input devices

mfd: adp5585: Add support for input devices

The ADP558x family supports a built in keypad matrix decoder which can
be added as an Input device. In order to both support the Input and the
GPIO device, we need to create a bitmap of the supported pins and track
their usage since they can either be used as GPIOs (GPIs) or as part of
the keymap.

We also need to mark special pins busy in case some features are being
used (ex: pwm or reset events).

Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20250701-dev-adp5589-fw-v7-14-b1fcfe9e9826@analog.com
Signed-off-by: Lee Jones <lee@kernel.org>