phylib: fix PAL state machine restart on resume

On resume, before starting the PAL state machine, check if the
adjust_link() method is well supplied. If not, this would lead to a
NULL pointer dereference in the phy_state_machine() function.

This scenario can happen if the Ethernet driver call manually the PHY
functions instead of using the PAL state machine. The mv643xx_eth driver
is a such example.

Signed-off-by: Simon Guinot <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/phy/mdio_bus.c

···
 	 * may call phy routines that try to grab the same lock, and that may
 	 * lead to a deadlock.
 	 */
-	if (phydev->attached_dev)
+	if (phydev->attached_dev && phydev->adjust_link)
 		phy_stop_machine(phydev);
 
 	if (!mdio_bus_phy_may_suspend(phydev))
···
 		return ret;
 
 no_resume:
-	if (phydev->attached_dev)
+	if (phydev->attached_dev && phydev->adjust_link)
 		phy_start_machine(phydev, NULL);
 
 	return 0;