pinctrl: baytrail: Allocate IRQ chip dynamic

Keeping the IRQ chip definition static shares it with multiple instances
of the GPIO chip in the system. This is bad and now we get this warning
from GPIO library:

"detected irqchip that is shared with multiple gpiochips: please fix the driver."

Hence, move the IRQ chip definition from being driver static into the struct
intel_pinctrl. So a unique IRQ chip is used for each GPIO chip instance.

Fixes: 9f573b98 ("pinctrl: baytrail: Update irq chip operations")
Depends-on: ca8a958e ("pinctrl: baytrail: Pass irqchip when adding gpiochip")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>