drivers: irq: fix compile warning

In the function gpio_get_intr_type, 'type' may be
used uninitialized if not add default process.

Change-Id: I917fecc2ed06cc844c30c93508084f32608edf6f
Signed-off-by: Jason Zhu <jason.zhu@rock-chips.com>

drivers/irq/irq-gpio.c

@@ -165,6 +165,8 @@ static int gpio_get_intr_type(void __iomem *regbase,
 	case 0x03:
 		type = GPIOEdgelRising;
 		break;
+	default:
+		type = -EINVAL;
 	}
 
 	return type;