gpio: pca9570: add a platform data structure

Add struct pca9570_platform_data for adding the platform data
structure. Also modify the existing structs for pca9570 and pca9571

Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@amd.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>