gpio: pca953x: store driver_data for future use

Instead of using id->driver_data directly we copied it to the internal
structure. This will help to adapt driver for ACPI use.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>