net: phy: call state machine synchronously in phy_stop

phy_stop() may be called e.g. when suspending, therefore all needed
actions should be performed synchronously. Therefore add a synchronous
call to the state machine.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>