net: phy: realtek: Check the index value in led_hw_control_get

Just like rtl8211f_led_hw_is_supported() and
rtl8211f_led_hw_control_set(), the rtl8211f_led_hw_control_get() also
needs to check the index value, otherwise the caller is likely to get
an incorrect rules.

Fixes: 17784801d8 ("net: phy: realtek: Add support for PHY LEDs on RTL8211F")
Signed-off-by: Hui Wang <hui.wang@canonical.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Link: https://patch.msgid.link/20240927114610.1278935-1-hui.wang@canonical.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/phy/realtek.c

@@ -527,6 +527,9 @@ static int rtl8211f_led_hw_control_get(struct phy_device *phydev, u8 index,
 {
 	int val;
 
+	if (index >= RTL8211F_LED_COUNT)
+		return -EINVAL;
+
 	val = phy_read_paged(phydev, 0xd04, RTL8211F_LEDCR);
 	if (val < 0)
 		return val;