irqchip/irq-rda-intc: Fix return value check in rda8810_intc_init()

In case of error, the function of_io_request_and_map() returns ERR_PTR()
and never returns NULL. The NULL test in the return value check should
be replaced with IS_ERR().

Fixes: d852e62ad689 ("irqchip: Add RDA8810PL interrupt driver")
Acked-by: Manivannan Sadhasivam <[e-mail]>
Signed-off-by: Wei Yongjun <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>

drivers/irqchip/irq-rda-intc.c

···
 				    struct device_node *parent)
 {
 	rda_intc_base = of_io_request_and_map(node, 0, "rda-intc");
-	if (!rda_intc_base)
-		return -ENXIO;
+	if (IS_ERR(rda_intc_base))
+		return PTR_ERR(rda_intc_base);
 
 	/* Mask all interrupt sources */
 	writel_relaxed(RDA_IRQ_MASK_ALL, rda_intc_base + RDA_INTC_MASK_CLR);