net: dsa: Do not clobber PHY link outside of state machine

Calling phy_read_status() means that we may call into
genphy_read_status() which in turn will use genphy_update_link() which
can make changes to phydev->link outside of the state machine's state
transitions. This is an invalid behavior that is now caught as of
811a9191 ("phy state machine: failsafe leave invalid RUNNING state")

Reported-by: Zefir Kurtisi <zefir.kurtisi@neratec.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>