amd-xgbe: Avoid spurious link down messages during interface toggle

During interface toggle operations (ifdown/ifup), the driver currently
resets the local helper variable 'phy_link' to -1. This causes the link
state machine to incorrectly interpret the state as a link change event,
resulting in spurious "Link is down" messages being logged when the
interface is brought back up.

Preserve the phy_link state across interface toggles to avoid treating
the -1 sentinel value as a legitimate link state transition.

Fixes: 88131a8 ("amd-xgbe: Perform phy connect/disconnect at dev open/stop")
Signed-off-by: Raju Rangoju <Raju.Rangoju@amd.com>
Reviewed-by: Dawid Osuchowski <dawid.osuchowski@linux.intel.com>
Link: https://patch.msgid.link/20251010065142.1189310-1-Raju.Rangoju@amd.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: RajuRangoju

drivers/net/ethernet/amd/xgbe/xgbe-drv.c

@@ -1080,7 +1080,6 @@ static void xgbe_free_rx_data(struct xgbe_prv_data *pdata)
 
 static int xgbe_phy_reset(struct xgbe_prv_data *pdata)
 {
-	pdata->phy_link = -1;
 	pdata->phy_speed = SPEED_UNKNOWN;
 
 	return pdata->phy_if.phy_reset(pdata);

drivers/net/ethernet/amd/xgbe/xgbe-mdio.c

@@ -1555,6 +1555,7 @@ static int xgbe_phy_init(struct xgbe_prv_data *pdata)
 		pdata->phy.duplex = DUPLEX_FULL;
 	}
 
+	pdata->phy_link = 0;
 	pdata->phy.link = 0;
 
 	pdata->phy.pause_autoneg = pdata->pause_autoneg;