gpio: adp5588: Add device tree support

Make platform data optional and add DT id table.
Switch to dynamically mapped GPIOs and IRQs if not provided
via platform data.

Signed-off-by: Nikolaus Voss <nikolaus.voss@loewensteinmedical.de>
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>