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 <dtor@chromium.org>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Tested-by: Kevin Cernekee <cernekee@gmail.com> 
Link: https://lkml.kernel.org/r/20141114221642.GA37468@dtor-wsSigned-off-by: Jason Cooper <jason@lakedaemon.net>

drivers/irqchip/irq-brcmstb-l2.c

@@ -135,9 +135,9 @@ int __init brcmstb_l2_intc_of_init(struct device_node *np,
 	__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;
 	}