irqchip/qcom: Fix error handling

'devm_ioremap()' returns NULL on error, not an error pointer.

Fixes: f20cc9b00c ("irqchip/qcom: Add IRQ combiner driver")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: marc.zyngier@arm.com
Cc: kernel-janitors@vger.kernel.org
Cc: jason@lakedaemon.net
Link: http://lkml.kernel.org/r/20170218083434.2289-1-christophe.jaillet@wanadoo.fr
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

drivers/irqchip/qcom-irq-combiner.c

@@ -202,9 +202,9 @@ static acpi_status get_registers_cb(struct acpi_resource *ares, void *context)
 	}
 
 	vaddr = devm_ioremap(ctx->dev, reg->address, REG_SIZE);
-	if (IS_ERR(vaddr)) {
+	if (!vaddr) {
 		dev_err(ctx->dev, "Can't map register @%pa\n", &paddr);
-		ctx->err = PTR_ERR(vaddr);
+		ctx->err = -ENOMEM;
 		return AE_ERROR;
 	}