staging: mt7621-gpio: avoid to set up irqs if not defined in dts

If there is no interrupt defined in the dts 'irq_of_parse_and_map'
returns 0 and we should't set up interrupts for each gpio chip in
that case.
Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/mt7621-gpio/gpio-mt7621.c

@@ -237,6 +237,7 @@ mediatek_gpio_bank_probe(struct platform_device *pdev, struct device_node *bank)
 		return ret;
 	}
 
+	if (gpio->gpio_irq) {
 		/*
 		 * Manually request the irq here instead of passing a flow-handler
 		 * to gpiochip_set_chained_irqchip, because the irq is shared.
@@ -260,6 +261,7 @@ mediatek_gpio_bank_probe(struct platform_device *pdev, struct device_node *bank)
 
 		gpiochip_set_chained_irqchip(&rg->chip, &mediatek_gpio_irq_chip,
 					     gpio->gpio_irq, NULL);
+	}
 
 	/* set polarity to low for all gpios */
 	mtk_gpio_w32(rg, GPIO_REG_POL, 0);