watchdog: sa1100: Fix PTR_ERR_OR_ZERO() vs NULL check in sa1100dog_probe()

devm_ioremap() doesn't return error pointers, it returns NULL on error.
Update the check accordingly.

Fixes: e86bd43 ("watchdog: sa1100: use platform device registration")
Signed-off-by: Chen Ni <nichen@iscas.ac.cn>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20240426075808.1582678-1-nichen@iscas.ac.cn
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

Author: Chen Ni

drivers/watchdog/sa1100_wdt.c

@@ -191,9 +191,8 @@ static int sa1100dog_probe(struct platform_device *pdev)
 	if (!res)
 		return -ENXIO;
 	reg_base = devm_ioremap(&pdev->dev, res->start, resource_size(res));
-	ret = PTR_ERR_OR_ZERO(reg_base);
-	if (ret)
-		return ret;
+	if (!reg_base)
+		return -ENOMEM;
 
 	clk = clk_get(NULL, "OSTIMER0");
 	if (IS_ERR(clk)) {