sysreset: syscon: update regmap access to syscon

Use new API syscon_node_to_regmap in sysreset_syscon driver
for compatible "syscon-reboot"; that's avoid the need of explicit
syscon binding for "regmap" handle.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/drivers/sysreset/sysreset_syscon.c b/drivers/sysreset/sysreset_syscon.c
index f19e80e..3450640 100644
--- a/drivers/sysreset/sysreset_syscon.c
+++ b/drivers/sysreset/sysreset_syscon.c
@@ -35,18 +35,20 @@
 
 int syscon_reboot_probe(struct udevice *dev)
 {
-	struct udevice *syscon;
 	struct syscon_reboot_priv *priv = dev_get_priv(dev);
 	int err;
+	u32 phandle;
+	ofnode node;
 
-	err = uclass_get_device_by_phandle(UCLASS_SYSCON, dev,
-					   "regmap", &syscon);
-	if (err) {
-		pr_err("unable to find syscon device\n");
+	err = ofnode_read_u32(dev_ofnode(dev), "regmap", &phandle);
+	if (err)
 		return err;
-	}
+
+	node = ofnode_get_by_phandle(phandle);
+	if (!ofnode_valid(node))
+		return -EINVAL;
 
-	priv->regmap = syscon_get_regmap(syscon);
+	priv->regmap = syscon_node_to_regmap(node);
 	if (!priv->regmap) {
 		pr_err("unable to find regmap\n");
 		return -ENODEV;