irqchip/irq-qcom-mpm: fix return value check in qcom_mpm_init()

If devm_platform_ioremap_resource() fails, it never returns
NULL, replace NULL check with IS_ERR().

Fixes: a6199bb ("irqchip: Add Qualcomm MPM controller driver")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220316025100.1758413-1-yangyingliang@huawei.com

drivers/irqchip/irq-qcom-mpm.c

@@ -375,7 +375,7 @@ static int qcom_mpm_init(struct device_node *np, struct device_node *parent)
 	raw_spin_lock_init(&priv->lock);
 
 	priv->base = devm_platform_ioremap_resource(pdev, 0);
-	if (!priv->base)
+	if (IS_ERR(priv->base))
 		return PTR_ERR(priv->base);
 
 	for (i = 0; i < priv->reg_stride; i++) {