net/phy: fix DP83865 10 Mbps HDX loopback disable function

According to the DP83865 datasheet "the 10 Mbps HDX loopback can be
disabled in the expanded memory register 0x1C0.1". The driver erroneously
used bit 0 instead of bit 1.

Fixes: 4621bf12 ("phy: Add file missed in previous commit.")
Signed-off-by: NPeter Mamonov <pmamonov@gmail.com>
Reviewed-by: NAndrew Lunn <andrew@lunn.ch>
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>

drivers/net/phy/national.c

@@ -105,14 +105,17 @@ static void ns_giga_speed_fallback(struct phy_device *phydev, int mode)
 
 static void ns_10_base_t_hdx_loopack(struct phy_device *phydev, int disable)
 {
+	u16 lb_dis = BIT(1);
+
 	if (disable)
-		ns_exp_write(phydev, 0x1c0, ns_exp_read(phydev, 0x1c0) | 1);
+		ns_exp_write(phydev, 0x1c0,
+			     ns_exp_read(phydev, 0x1c0) | lb_dis);
 	else
 		ns_exp_write(phydev, 0x1c0,
-			     ns_exp_read(phydev, 0x1c0) & 0xfffe);
+			     ns_exp_read(phydev, 0x1c0) & ~lb_dis);
 
 	pr_debug("10BASE-T HDX loopback %s\n",
-		 (ns_exp_read(phydev, 0x1c0) & 0x0001) ? "off" : "on");
+		 (ns_exp_read(phydev, 0x1c0) & lb_dis) ? "off" : "on");
 }
 
 static int ns_config_init(struct phy_device *phydev)