pinctrl: cherryview: Split out irq hw-init into a separate helper function

Split out irq hw-init into a separate chv_gpio_irq_init_hw() function.
This is a preparation patch for passing the irqchip when adding the
gpiochip.

Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>