irqchip/ompic: fix return value check in ompic_of_init()

In case of error, the function ioremap() returns NULL pointer not
ERR_PTR(). The IS_ERR() test in the return value check should be
replaced with NULL test.

Fixes: 9b54470afd83 ("irqchip: add initial support for ompic")
Acked-by: Stafford Horne <shorne@gmail.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

drivers/irqchip/irq-ompic.c

@@ -171,9 +171,9 @@ static int __init ompic_of_init(struct device_node *node,
 
 	/* Setup the device */
 	ompic_base = ioremap(res.start, resource_size(&res));
-	if (IS_ERR(ompic_base)) {
+	if (!ompic_base) {
 		pr_err("ompic: unable to map registers");
-		return PTR_ERR(ompic_base);
+		return -ENOMEM;
 	}
 
 	irq = irq_of_parse_and_map(node, 0);