irqchip: mtk-sysirq: Make mtk_sysirq_of_init return error if ioremap fails

PTR_ERR(NULL) returns 0 so current code returns 0 if ioremap fails, fix it.

Signed-off-by: Axel Lin <[e-mail]>
Reviewed-by: Matthias Brugger <[e-mail]>
Cc: Yingjoe Chen <[e-mail]>
Cc: [e-mail] <[e-mail]>
Cc: Jason Cooper <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Thomas Gleixner <[e-mail]>

drivers/irqchip/irq-mtk-sysirq.c

···
 	chip_data->intpol_base = ioremap(res.start, size);
 	if (!chip_data->intpol_base) {
 		pr_err("mtk_sysirq: unable to map sysirq register\n");
-		ret = PTR_ERR(chip_data->intpol_base);
+		ret = -ENXIO;
 		goto out_free;
 	}