gpio: tangier: Use correct type for the IRQ chip data

IRQ chip data contains a pointer to the GPIO chip. Luckily we have
the pointers the same, but strictly speaking it's not guaranteed.
Even though, still better to fix this.

Fixes: ccf6fd6d ("gpio: merrifield: Introduce GPIO driver to support Merrifield")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>