hwspinlock: fix return value check in stm32_hwspinlock_probe()

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

Fixes: f24fcff1d2 ("hwspinlock: add STM32 hwspinlock device")
Acked-by: Benjamin Gaignard <benjamin.gaignard@gmail.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/hwspinlock/stm32_hwspinlock.c

@@ -57,8 +57,8 @@ static int stm32_hwspinlock_probe(struct platform_device *pdev)
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	io_base = devm_ioremap_resource(&pdev->dev, res);
-	if (!io_base)
-		return -ENOMEM;
+	if (IS_ERR(io_base))
+		return PTR_ERR(io_base);
 
 	array_size = STM32_MUTEX_NUM_LOCKS * sizeof(struct hwspinlock);
 	hw = devm_kzalloc(&pdev->dev, sizeof(*hw) + array_size, GFP_KERNEL);