ixgbe: Use MDIO_PRTAD_NONE consistently

The value MDIO_PRTAD_NONE should be used to indicate no PHY address.
Not 0, not 0xFFFF. Use the MDIO_PRTAD_NONE value consistently.

Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_phy.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_phy.c
index db0731e..021ab9b 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_phy.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_phy.c
@@ -346,8 +346,8 @@
 				return 0;
 			}
 		}
-		/* clear value if nothing found */
-		hw->phy.mdio.prtad = 0;
+		/* indicate no PHY found */
+		hw->phy.mdio.prtad = MDIO_PRTAD_NONE;
 		return IXGBE_ERR_PHY_ADDR_INVALID;
 	}
 	return 0;
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_x550.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_x550.c
index cd22efb..7e6b926 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_x550.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_x550.c
@@ -1459,7 +1459,7 @@
 	/* Configure internal PHY for KR/KX. */
 	ixgbe_setup_kr_speed_x550em(hw, speed);
 
-	if (!hw->phy.mdio.prtad || hw->phy.mdio.prtad == 0xFFFF)
+	if (hw->phy.mdio.prtad == MDIO_PRTAD_NONE)
 		return IXGBE_ERR_PHY_ADDR_INVALID;
 
 	/* Get external PHY device id */