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

BugLink: https://bugs.launchpad.net/bugs/1848589

[ Upstream commit e47488b2 ]

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: Peter Mamonov <pmamonov@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/net/phy/national.c

@@ -110,14 +110,17 @@ 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)