irqchip/ls-extirq: Fix devm_of_iomap() error check

The devm_of_iomap() function returns an ERR_PTR() encoded error code on
failure. Replace the incorrect check against NULL with IS_ERR().

Fixes: 05cd654829dd ("irqchip/ls-extirq: Convert to a platform driver to make it work again")
Reported-by: Dan Carpenter <[e-mail]>
Signed-off-by: Ioana Ciornei <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Reviewed-by: Herve Codina <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Closes: https://lore.kernel.org/all/[e-mail]/

drivers/irqchip/irq-ls-extirq.c

···
 		return dev_err_probe(dev, -ENOMEM, "Failed to allocate memory\n");
 
 	priv->intpcr = devm_of_iomap(dev, node, 0, NULL);
-	if (!priv->intpcr)
-		return dev_err_probe(dev, -ENOMEM, "Cannot ioremap OF node %pOF\n", node);
+	if (IS_ERR(priv->intpcr)) {
+		return dev_err_probe(dev, PTR_ERR(priv->intpcr),
+				     "Cannot ioremap OF node %pOF\n", node);
+	}
 
 	ret = ls_extirq_parse_map(priv, node);
 	if (ret)