net: phy: ensure phylib state machine is stopped after calling phy_stop

The call to the phylib state machine in phy_stop() just ensures that
the state machine isn't re-triggered, but a state machine call may
be scheduled already. So lets's call phy_stop_machine().
This also allows to get rid of the call to phy_stop_machine() in
phy_disconnect().

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>