net: phy: Use interrupts when available in NOLINK state

The NOLINK state will poll the phy once a second to see if the link
has come up. If the phy has an interrupt line, this polling can be
skipped, since the phy should interrupt when the link returns.
Signed-off-by: NAndrew Lunn <andrew@lunn.ch>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/phy/phy.c

@@ -863,6 +863,9 @@ void phy_state_machine(struct work_struct *work)
 			needs_aneg = true;
 		break;
 	case PHY_NOLINK:
+		if (phy_interrupt_is_valid(phydev))
+			break;
+
 		err = phy_read_status(phydev);
 		if (err)
 			break;