usb: onboard-hub: Fix the return values of regulator APIs

Don't error out if there is no vdd regulator supply, as these are
optional properties.

Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@amd.com>
Reviewed-by: Marek Vasut <marex@denx.de>
diff --git a/common/usb_onboard_hub.c b/common/usb_onboard_hub.c
index e4d1f12..812e774 100644
--- a/common/usb_onboard_hub.c
+++ b/common/usb_onboard_hub.c
@@ -57,14 +57,18 @@
 	int ret;
 
 	ret = device_get_supply_regulator(dev, "vdd-supply", &hub->vdd);
-	if (ret) {
+	if (ret && ret != -ENOENT) {
 		dev_err(dev, "can't get vdd-supply: %d\n", ret);
 		return ret;
 	}
 
-	ret = regulator_set_enable_if_allowed(hub->vdd, true);
-	if (ret)
-		dev_err(dev, "can't enable vdd-supply: %d\n", ret);
+	if (hub->vdd) {
+		ret = regulator_set_enable_if_allowed(hub->vdd, true);
+		if (ret && ret != -ENOSYS) {
+			dev_err(dev, "can't enable vdd-supply: %d\n", ret);
+			return ret;
+		}
+	}
 
 	return usb_onboard_hub_reset(dev);
 }