irqchip: brcmstb-l2: Fix error handling of irq_of_parse_and_map

Return value of irq_of_parse_and_map() is unsigned int, with 0
indicating failure, so testing for negative result never works.

Signed-off-by: Dmitry Torokhov <[e-mail]>
Acked-by: Florian Fainelli <[e-mail]>
Tested-by: Kevin Cernekee <[e-mail]>
Link: https://lkml.kernel.org/r/20141114221642.GA37468@dtor-ws
Signed-off-by: Jason Cooper <[e-mail]>

drivers/irqchip/irq-brcmstb-l2.c

···
 	__raw_writel(0xffffffff, data->base + CPU_CLEAR);
 
 	data->parent_irq = irq_of_parse_and_map(np, 0);
-	if (data->parent_irq < 0) {
+	if (!data->parent_irq) {
 		pr_err("failed to find parent interrupt\n");
-		ret = data->parent_irq;
+		ret = -EINVAL;
 		goto out_unmap;
 	}