watchdog: lenovo_se30_wdt: Fix possible devm_ioremap() NULL pointer dereference in lenovo_se30_wdt_probe()

devm_ioremap() returns NULL on error. Currently, lenovo_se30_wdt_probe()
does not check for this case, which results in a NULL pointer
dereference.

Add NULL check after devm_ioremap() to prevent this issue.

Fixes: c284153 ("watchdog: lenovo_se30_wdt: Watchdog driver for Lenovo SE30 platform")
Signed-off-by: Henry Martin <bsdhenrymartin@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20250424071648.89016-1-bsdhenrymartin@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

Author: Henry Martin

drivers/watchdog/lenovo_se30_wdt.c

@@ -271,6 +271,8 @@ static int lenovo_se30_wdt_probe(struct platform_device *pdev)
 		return -EBUSY;
 
 	priv->shm_base_addr = devm_ioremap(dev, base_phys, SHM_WIN_SIZE);
+	if (!priv->shm_base_addr)
+		return -ENOMEM;
 
 	priv->wdt_cfg.mod = WDT_MODULE;
 	priv->wdt_cfg.idx = WDT_CFG_INDEX;