gpio: pca953x: add support for pca6416

The NXP PCA6416, documented at [1], is a variant of the PCA GPIO
expander with 16 GPIOs, and supporting an interrupt.

[1] https://www.nxp.com/docs/en/data-sheet/PCA6416A.pdf



Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>