gpio: siox: explicitly support only threaded irqs

The gpio-siox driver uses handle_nested_irq() to implement its
interrupt support. This is only capable of handling threaded irq
actions. For a hardirq action it triggers a NULL pointer oops.
(It calls action->thread_fn which is NULL then.)

Prevent registration of a hardirq action by setting
gpio_irq_chip::threaded to true.

Cc: [e-mail]
Fixes: be8c8facc707 ("gpio: new driver to work with a 8x12 siox")
Cc: [e-mail]
Signed-off-by: Ahmad Fatoum <[e-mail]>
Acked-by: Uwe Kleine-König <[e-mail]>
Signed-off-by: Bartosz Golaszewski <[e-mail]>

drivers/gpio/gpio-siox.c

···
 	girq->chip = &ddata->ichip;
 	girq->default_type = IRQ_TYPE_NONE;
 	girq->handler = handle_level_irq;
+	girq->threaded = true;
 
 	ret = devm_gpiochip_add_data(dev, &ddata->gchip, NULL);
 	if (ret)