sysreset: syscon: Don't assume default value for offset and mask property

Per the DT binding, <offset> is a required property. Let's abort
the probe if it is missing. For the <mask> property, current codes
assume a default value of zero, which is not correct either.
Signed-off-by: NBin Meng <bin.meng@windriver.com>
Reviewed-by: NSimon Glass <sjg@chromium.org>
Reviewed-by: NPragnesh Patel <pragnesh.patel@sifive.com>

drivers/sysreset/sysreset_syscon.c

@@ -41,6 +41,7 @@ static struct sysreset_ops syscon_reboot_ops = {
 int syscon_reboot_probe(struct udevice *dev)
 {
 	struct syscon_reboot_priv *priv = dev_get_priv(dev);
+	int err;
 
 	priv->regmap = syscon_regmap_lookup_by_phandle(dev, "regmap");
 	if (IS_ERR(priv->regmap)) {
@@ -48,8 +49,17 @@ int syscon_reboot_probe(struct udevice *dev)
 		return -ENODEV;
 	}
 
-	priv->offset = dev_read_u32_default(dev, "offset", 0);
-	priv->mask = dev_read_u32_default(dev, "mask", 0);
+	err = dev_read_u32(dev, "offset", &priv->offset);
+	if (err) {
+		pr_err("unable to find offset\n");
+		return -ENOENT;
+	}
+
+	err = dev_read_u32(dev, "mask", &priv->mask);
+	if (err) {
+		pr_err("unable to find mask\n");
+		return -ENOENT;
+	}
 
 	return 0;
 }