net: phy: Fix reading LED reg property

'reg' is always encoded in 32 bits, thus it has to be read using the
function with the corresponding bit width.

Fixes: 01e5b72 ("net: phy: Add a binding for PHY LEDs")
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20230424141648.317944-1-alexander.stein@ew.tq-group.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: tq-steina

drivers/net/phy/phy_device.c

@@ -3028,6 +3028,7 @@ static int of_phy_led(struct phy_device *phydev,
 	struct led_init_data init_data = {};
 	struct led_classdev *cdev;
 	struct phy_led *phyled;
+	u32 index;
 	int err;
 
 	phyled = devm_kzalloc(dev, sizeof(*phyled), GFP_KERNEL);
@@ -3037,10 +3038,13 @@ static int of_phy_led(struct phy_device *phydev,
 	cdev = &phyled->led_cdev;
 	phyled->phydev = phydev;
 
-	err = of_property_read_u8(led, "reg", &phyled->index);
+	err = of_property_read_u32(led, "reg", &index);
 	if (err)
 		return err;
+	if (index > U8_MAX)
+		return -EINVAL;
 
+	phyled->index = index;
 	if (phydev->drv->led_brightness_set)
 		cdev->brightness_set_blocking = phy_led_set_brightness;
 	if (phydev->drv->led_blink_set)