platform/x86: hp-wmi: Convert simple_strtoul() to kstrtou32()

First of all, unsigned long can overflow u32 value on 64-bit machine.
Second, simple_strtoul() doesn't check for overflow in the input.

Convert simple_strtoul() to kstrtou32() to eliminate above issues.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/platform/x86/hp-wmi.c

@@ -461,8 +461,14 @@ static ssize_t postcode_show(struct device *dev, struct device_attribute *attr,
 static ssize_t als_store(struct device *dev, struct device_attribute *attr,
 			 const char *buf, size_t count)
 {
-	u32 tmp = simple_strtoul(buf, NULL, 10);
-	int ret = hp_wmi_perform_query(HPWMI_ALS_QUERY, HPWMI_WRITE, &tmp,
+	u32 tmp;
+	int ret;
+
+	ret = kstrtou32(buf, 10, &tmp);
+	if (ret)
+		return ret;
+
+	ret = hp_wmi_perform_query(HPWMI_ALS_QUERY, HPWMI_WRITE, &tmp,
 				       sizeof(tmp), sizeof(tmp));
 	if (ret)
 		return ret < 0 ? ret : -EINVAL;