pinctrl: baytrail: Group GPIO IRQ chip initialization

After commit 5ea422750a9f ("pinctrl: baytrail: Pass irqchip when
adding gpiochip") the GPIO IRQ chip structure is being initialized
under conditional when IRQ resource has been discovered. But that
commit left aside the assignment of ->init_valid_mask() callback
that is done unconditionally.

For sake of consistency and preventing some garbage in GPIO IRQ chip
structure group initialization together.

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